| 1. |
- Marganiec, C., et al.
(författare)
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Coulomb breakup of 17Ne from the viewpoint of nuclear astrophysics
- 2013
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Ingår i: Proceedings of Science.
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Konferensbidrag (refereegranskat)abstract
- By the Coulomb breakup of 17Ne, the time-reversed reaction 15O(2p,γ)17Ne has been studied. This reaction might play an important role in the rp process, as a break-out reaction of the hot CNO cycle. The secondary 17Ne ion beam with an energy of 500 MeV/nucleon has been dissociated in a Pb target. The reaction products have been detected with the LAND-R3B experimental setup at GSI. The preliminary differential and integral Coulomb dissociation cross section sCoul has been determined, which then will be converted into a photo-absorption cross section sphot o, and a two-proton radiative capture cross section σcap. Additionally, information about the structure of the 17Ne, a potential two-proton halo nucleus, will be received. The analysis is in progress.
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| 2. |
- van Sorge, Nina M., et al.
(författare)
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Bacterial protein domains with a novel Ig-like fold target human CEACAM receptors
- 2021
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Ingår i: EMBO Journal. - : Wiley-VCH Verlagsgesellschaft. - 0261-4189 .- 1460-2075. ; 40
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Tidskriftsartikel (refereegranskat)abstract
- Streptococcus agalactiae, also known as group B Streptococcus (GBS), is the major cause of neonatal sepsis in humans. A critical step to infection is adhesion of bacteria to epithelial surfaces. GBS adhesins have been identified to bind extracellular matrix components and cellular receptors. However, several putative adhesins have no host binding partner characterised. We report here that surface-expressed β protein of GBS binds to human CEACAM1 and CEACAM5 receptors. A crystal structure of the complex showed that an IgSF domain in β represents a novel Ig-fold subtype called IgI3, in which unique features allow binding to CEACAM1. Bioinformatic assessment revealed that this newly identified IgI3 fold is not exclusively present in GBS but is predicted to be present in adhesins from other clinically important human pathogens. In agreement with this prediction, we found that CEACAM1 binds to an IgI3 domain found in an adhesin from a different streptococcal species. Overall, our results indicate that the IgI3 fold could provide a broadly applied mechanism for bacteria to target CEACAMs.
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| 3. |
- Aksyutina, Yuliya, 1983, et al.
(författare)
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Properties of the 7He ground state from 8He neutron knockout
- 2009
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693. ; 679:3, s. 191-196
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Tidskriftsartikel (refereegranskat)abstract
- The unbound nucleus 7He, produced in neutron-knockout reactions with a 240 MeV/u 8He beam in a liquid-hydrogen target, has been studied in an experiment at the ALADIN-LAND setup at GSI. From an R-matrix analysis the resonance parameters for 7He as well as the spectroscopic factor for the 6He(0+) + n configuration in its ground-state have been obtained. The spectroscopic factor is 0.61 confirming that 7He is not a pure single-particle state. An analysis of 5He data from neutron-knockout reactions of 6He in a carbon target reveals the presence of an s-wave component at low energies in the α+n relative energy spectrum. A possible low-lying exited state in 7He observed in neutron knockout data from 8He in a carbon target and tentatively interpreted as a Iπ=1/2− state, could not be observed in the present experiment. Possible explanations of the shape difference between the 7He resonance obtained in the two knockout reactions are discussed in terms of target-dependence or different reaction mechanisms at relativistic energies.
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| 4. |
- Alrifaiy, Ahmed, et al.
(författare)
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A lab-on-a-chip for hypoxic patch clamp measurements combined with optical tweezers and spectroscopy : first investigations of single biological cells
- 2015
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Ingår i: Biomedical engineering online. - : Springer Science and Business Media LLC. - 1475-925X. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The response and the reaction of the brain system to hypoxia is a vital research subject that requires special instrumentation. With this research subject in focus, a new multifunctional lab-on-a-chip (LOC) system with control over the oxygen content for studies on biological cells was developed. The chip was designed to incorporate the patch clamp technique, optical tweezers and absorption spectroscopy. The performance of the LOC was tested by a series of experiments. The oxygen content within the channels of the LOC was monitored by an oxygen sensor and verified by simultaneously studying the oxygenation state of chicken red blood cells (RBCs) with absorption spectra. The chicken RBCs were manipulated optically and steered in three dimensions towards a patch-clamp micropipette in a closed microfluidic channel. The oxygen level within the channels could be changed from a normoxic value of 18% O 2 to an anoxic value of 0.0-0.5% O 2. A time series of 3 experiments were performed, showing that the spectral transfer from the oxygenated to the deoxygenated state occurred after about 227 ± 1 s and a fully developed deoxygenated spectrum was observed after 298 ± 1 s, a mean value of 3 experiments. The tightness of the chamber to oxygen diffusion was verified by stopping the flow into the channel system while continuously recording absorption spectra showing an unchanged deoxygenated state during 5400 ± 2 s. A transfer of the oxygenated absorption spectra was achieved after 426 ± 1 s when exposing the cell to normoxic buffer. This showed the long time viability of the investigated cells. Successful patching and sealing were established on a trapped RBC and the whole-cell access (Ra) and membrane (Rm) resistances were measured to be 5.033 ± 0.412 M Ω and 889.7 ± 1.74 M Ω respectively.
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| 5. |
- Alrifaiy, Ahmed, et al.
(författare)
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Polymer-based microfluidic devices for pharmacy, biology and tissue engineering
- 2012
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Ingår i: Polymers. - : MDPI AG. - 2073-4360. ; 4:3, s. 1349-1398
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Forskningsöversikt (refereegranskat)abstract
- This paper reviews microfluidic technologies with emphasis on applications in the fields of pharmacy, biology, and tissue engineering. Design and fabrication of microfluidic systems are discussed with respect to specific biological concerns, such as biocompatibility and cell viability. Recent applications and developments on genetic analysis, cell culture, cell manipulation, biosensors, pathogen detection systems, diagnostic devices, high-throughput screening and biomaterial synthesis for tissue engineering are presented. The pros and cons of materials like polydimethylsiloxane (PDMS), polymethylmethacrylate (PMMA), polystyrene (PS), polycarbonate (PC), cyclic olefin copolymer (COC), glass, and silicon are discussed in terms of biocompatibility and fabrication aspects. Microfluidic devices are widely used in life sciences. Here, commercialization and research trends of microfluidics as new, easy to use, and cost-effective measurement tools at the cell/tissue level are critically reviewed.
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| 6. |
- Eklund, Anders, et al.
(författare)
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Evaluation of applanation resonator sensors for intra-ocular pressure measurement : results from clinical and in vitro studies.
- 2003
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 41:2, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- Glaucoma is an eye disease that, in its most common form, is characterised by high intra-ocular pressure (IOP), reduced visual field and optic nerve damage. For diagnostic purposes and for follow-up after treatment, it is important to have simple and reliable methods for measuring IOP. Recently, an applanation resonator sensor (ARS) for measuring IOP was introduced and evaluated using an in vitro pig-eye model. In the present study, the first clinical evaluation of the same probe has been carried out, with experiments in vivo on human eyes. There was a low but significant correlation between IOP(ARS) and the IOP measured with a Goldmann applanation tonometer (r = 0.40, p = 0.001, n = 72). However, off-centre positioning of the sensor against the cornea caused a non-negligible source of error. The sensor probe was redesigned to have a spherical, instead of flat, contact surface against the eye and was evaluated in the in vitro model. The new probe showed reduced sensitivity to off-centre positioning, with a decrease in relative deviation from 89% to 11% (1 mm radius). For normalised data, linear regression between IOP(ARS) and direct IOP measurement in the vitreous chamber showed a correlation of r = 0.97 (p < 0.001, n = 108) and a standard deviation for the residuals of SD < or = 2.18 mm Hg (n = 108). It was concluded that a spherical contact surface should be preferred and that further development towards a clinical instrument should focus on probe design and signal analysis.
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| 7. |
- Hallberg, Per, et al.
(författare)
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Applanation resonance tonometry for intraocular pressure in humans
- 2004
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Ingår i: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 25:4, s. 1053-1065
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Tidskriftsartikel (refereegranskat)abstract
- Glaucoma is a group of diseases associated with optic nerve damage and loss of visual field. The aetiology is not completely understood, but one of the major risk factors is elevated intraocular pressure (IOP). Reliable methods for measuring the IOP are therefore important. The aim of the study was to investigate the ability of the applanation resonance tonometry (ART) system, based on continuous force and area recording, to measure IOP in humans. Both the phase of initial indentation (IOPIndentation) and the phase when the sensor was removed (IOPRemoval) from the cornea were analysed. The Goldmann applanation tonometry (GAT) was used as reference method. The study included 24 healthy volunteers with normal IOP and 24 patients with elevated IOP. The correlation and standard deviation (SD) between IOPIndentation and IOPGAT was R = 0.92 (p < 0.001), SD = 3.6 mmHg, n = 104, and between IOPRemoval and IOPGAT R = 0.94 (p < 0.001), SD = 3.1 mmHg, n = 104. In conclusion, resonance sensor technology has made it possible to introduce a new multi-point method for measuring IOP, and the method is relevant for measuring IOP in humans. The study indicates that with further development towards elimination of position dependence, the ART has the potential to become a useful clinical instrument for IOP measurement.
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| 8. |
- Hallberg, Per, 1965-
(författare)
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Applanation Resonance Tonometry for Intraocular Pressure Measurement
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Elevated intraocular pressure (IOP) is one of the major risk factors for glaucoma. Since glaucoma is a leading cause of blindness, reliable methods for measuring the IOP are important. This doctoral dissertation presents a new method, applanation resonance tonometry (ART), for measurement of IOP. The method is based on resonance sensor technology combined with the novel multipoint analysis of continuously sampled data of both contact force and contact area. The ART was evaluated in in vitro porcine-eye studies as well as in clinic on both healthy volunteers and patients. A new symmetric probe with a larger sensor tip and improved aligning light was developed and evaluated in vitro. It showed that the error from off-centring was highly reduced. The new ART probe, used as a biomicroscope device (ARTBiom) and as a handheld device (ARTHand), was further evaluated in a clinical study designed in accordance with the International Standard Organisation’s (ISO) requirement. Both the ARTBiom and the ARTHand met the precision set by the requirements. Laser surgery is a common way to correct vision. The biomechanical effect of photorefractive keratectomy (PRK) on IOP measurements was evaluated using Goldmann applanation tonometry (GAT) and ART in an in vitro study. Both methods were affected, but to a different extent. The flat contact probe of GAT, as compared with the convex tip of ART, and single point vs. multipoint approach, provide explanation to the ART advantage regarding measurement error of IOP after PRK. In conclusion, resonance sensor technology has made it possible to introduce a new multipoint method for measuring IOP, and the method is relevant for measuring IOP in humans. It may be possible to reduce errors in the clinical measurement of IOP with this new method, especially after corneal surgery. The ART has the potential to become a useful clinical instrument for IOP measurement.
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| 9. |
- Hallberg, Per, et al.
(författare)
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Underestimation of intraocular pressure after photorefractive keratectomy : a biomechanical analysis
- 2006
-
Ingår i: Medical and Biological Engineering and Computing. - : Springer. - 0140-0118 .- 1741-0444. ; 44, s. 609-618
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Tidskriftsartikel (refereegranskat)abstract
- Excimer laser surgery, to correct corneal refraction, induces changes in corneal thickness and curvature. Both factors can cause measurement errors when determining intraocular pressure (IOP). This study evaluates effects of photorefractive keratectomy (PRK) on IOP measurements, using Goldmann applanation tonometry (GAT) and Applanation resonance tonometry (ART), in an in vitro model. Six porcine eyes was enucleated and pressurised to a constant IOP = 30 mmHg. After removal of the epithelium, the eyes were PRK-treated for a total of 25 dioptres. The measured IOP decreased 13.2 mmHg for GAT and 9.0 mmHg for ART. The total underestimation by GAT was larger than for ART, and a part of the ART underestimation (3.5 mmHg) was assigned to sensitivity to the change in corneal surface structure resulting from the removal of epithelium. The flat contact probe of GAT, as compared with the convex tip of ART, provided explanation for the difference in IOP measurement error after PRK.
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| 10. |
- Hu, Xiao-Lei, et al.
(författare)
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Assessments of a novel digital follow-up tool Rehabkompassen® to identify rehabilitation needs among stroke patients in an outpatient setting
- 2022
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Ingår i: Digital Health. - : Sage Publications. - 2055-2076. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: It remains a huge challenge to identify individual rehabilitation needs in a time-efficient manner for providing patient-tailored rehabilitation during the continuum of stroke care. We have recently demonstrated the usefulness of a paper-version Rehab-Compass as a follow-up tool. The aim of the current study was to develop a digital version of the Rehab-Compass and evaluate its usability and feasibility.Methods: The novel digital tool Rehabkompassen® was developed by an iterative and participatory design process. Patients' rehabilitation needs were visualized by the tool and used before, during, and after the consultation. The usability and feasibility of the tool was assessed by task completion rate, the System Usability Scale, and satisfaction questionnaires among 2 physicians and 24 adult stroke patients in an outpatient clinical setting.Results: Rehabkompassen® identified and graphically visualized a panoramic view of the stroke patients' multidimensional needs in individual- and group levels. The instrument appeared to be feasible and time efficient in clinical use with a 100% overall task completion rate for both patients and physicians. A majority of the patients reported that it was very easy or fairly easy to answer the digital questionnaires and to understand their own digital Rehab-Compass graph. Two physicians reported a high mean score on the System Usability Scale (95/100) and were positive about using the tool in the future.Conclusions: The current results indicated that Rehabkompassen® was a feasible, useful, and time-saving follow-up tool for the identification of rehabilitation needs among stroke survivors in the post-acute continuum of care after stroke. Further research is needed to evaluate the efficacy of the digital instrument among stroke patients.
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| 11. |
- Hu, Xiao-Lei, et al.
(författare)
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Digital Graphic Follow-up Tool (Rehabkompassen) for Identifying Rehabilitation Needs among People after Stroke : Randomized Clinical Feasibility Study
- 2022
-
Ingår i: JMIR Human Factors. - : JMIR Publications. - 2292-9495. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Background: Stroke is a leading cause of disability among adults, with heavy social and economic burden worldwide. A cost-effective solution is urgently needed to facilitate the identification of individual rehabilitation needs and thereby provide tailored rehabilitations to reduce disability among people who have had a stroke. A novel digital graphic follow-up tool Rehabkompassen has recently been developed to facilitate capturing the multidimensional rehabilitation needs of people who have had a stroke.Objective: The aim of this study was to evaluate the feasibility and acceptability of conducting a definitive trial to evaluate Rehabkompassen as a digital follow-up tool among people who have had a stroke in outpatient clinical settings.Methods: This pilot study of Rehabkompassen was a parallel, open-label, 2-arm prospective, proof-of-concept randomized controlled trial (RCT) with an allocation ratio of 1:1 in a single outpatient clinic. Patients who have had a stroke within the 3 previous months, aged ≥18 years, and living in the community were included. The trial compared usual outpatient visits with Rehabkompassen (intervention group) and without Rehabkompassen (control group) at the 3-month follow-up as well as usual outpatient visit with Rehabkompassen at the 12-month follow-up. Information on the recruitment rate, delivery, and uptake of Rehabkompassen; assessment and outcome measures completion rates; the frequency of withdrawals; the loss of follow-up; and satisfaction scores were obtained. The key outcomes were evaluated in both groups.Results: In total, 28 patients (14 control, 14 Rehabkompassen) participated in this study, with 100 patients screened. The overall recruitment rate was 28% (28/100). Retention in the trial was 86% (24/28) at the 12-month follow-up. All participants used the tool as planned during their follow-ups, which provided a 100% (24/24) task completion rate of using Rehabkompassen and suggested excellent feasibility. Both patient- and physician-participants reported satisfaction with the instrument (19/24, 79% and 2/2, 100%, respectively). In all, 2 (N=2, 100%) physicians and 18 (N=24, 75%) patients were willing to use the tool in the future. Furthermore, modified Rankin Scale as the primary outcome and various stroke impacts as secondary outcomes were both successfully collected and compared in this study.Conclusions: This study demonstrated the high feasibility and adherence of the study protocol as well as the high acceptability of Rehabkompassen among patients who have had a stroke and physicians in an outpatient setting in comparison to the predefined criterion. The information collected in this feasibility study combined with the amendments of the study protocol may improve the future definitive RCT. The results of this trial support the feasibility and acceptability of conducting a large definitive RCT.
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| 12. |
- Hu, Xiao-Lei, et al.
(författare)
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Study protocol for a randomized, controlled, multicentre, pragmatic trial with Rehabkompassen®-a digital structured follow-up tool for facilitating patient-tailored rehabilitation in persons after stroke
- 2023
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Ingår i: Trials. - : BioMed Central (BMC). - 1745-6215. ; 24:1
-
Tidskriftsartikel (refereegranskat)abstract
- BackgroundStroke is a leading cause of disability among adults worldwide. A timely structured follow-up tool to identify patients' rehabilitation needs and develop patient-tailored rehabilitation regimens to decrease disability is largely lacking in current stroke care. The overall purpose of this study is to evaluate the effectiveness of a novel digital follow-up tool, Rehabkompassen (R), among persons discharged from acute care settings after a stroke.MethodsThis multicentre, parallel, open-label, two-arm pragmatic randomized controlled trial with an allocation ratio of 1:1 will be conducted in Sweden. A total of 1106 adult stroke patients will have follow-up visits in usual care settings at 3 and 12 months after stroke onset. At the 3-month follow-up, participants will have a usual outpatient visit without (control group, n = 553) or with (intervention group, n = 553) the Rehabkompassen (R) tool. All participants will receive the intervention at the 12-month follow-up visit. Feedback from the end-users (patient and health care practitioners) will be collected after the visits. The primary outcomes will be the patients' independence and social participation at the 12-month visits. Secondary outcomes will include end-users' satisfaction, barriers and facilitators for adopting the instrument, other stroke impacts, health-related quality of life and the cost-effectiveness of the instrument, calculated by incremental cost per quality-adjusted life year (QALY).DiscussionThe outcomes of this trial will inform clinical practice and health care policy on the role of the Rehabkompassen (R) digital follow-up tool in the post-acute continuum of care after stroke.Trial registrationClinicalTrials.gov NCT04915027. Registered on 4 June 2021. ISRCTN registry ISRCTN63166587. Registered on 21 August 2023.
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| 13. |
- Jalkanen, Ville, 1978-, et al.
(författare)
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Prostate tissue stiffness as measured with a resonance sensor system : a study on silicone and human prostate tissue in vitro.
- 2006
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Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 44:7, s. 593-603
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Tidskriftsartikel (refereegranskat)abstract
- Prostate cancer is the most common form of cancer in men in Europe and in the USA. Some prostate tumours are stiffer than the surrounding normal tissue, and it could therefore be of interest to measure prostate tissue stiffness. Resonance sensor technology based on piezoelectric resonance detects variations in tissue stiffness due to a change in the resonance frequency. An impression-controlled resonance sensor system was used to detect stiffness in silicone rubber and in human prostate tissue in vitro using two parameters, both combinations of frequency change and force. Variations in silicone rubber stiffness due to the mixing ratio of the two components could be detected (p<0.05) using both parameters. Measurements on prostate tissue showed that there existed a statistically significant (MANOVA test, p<0.001) reproducible difference between tumour tissue (n=13) and normal healthy tissue (n=98) when studying a multivariate parameter set. Both the tumour tissue and normal tissue groups had variations within them, which were assumed to be related to differences in tissue composition. Other sources of error could be uneven surfaces and different levels of dehydration for the prostates. Our results indicated that the resonance sensor could be used to detect stiffness variations in silicone and in human prostate tissue in vitro. This is promising for the development of a future diagnostic tool for prostate cancer.
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| 14. |
- Jalkanen, Ville, 1978-, et al.
(författare)
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Resonance sensor measurements of stiffness variations in prostate tissue in vitro : a weighted tissue proportion model
- 2006
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Ingår i: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 27:12, s. 1373-86
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Tidskriftsartikel (refereegranskat)abstract
- Prostate cancer is the most common type of cancer in men in Europe and the US. The methods to detect prostate cancer are still precarious and new techniques are needed. A piezoelectric transducer element in a feedback system is set to vibrate with its resonance frequency. When the sensor element contacts an object a change in the resonance frequency is observed, and this feature has been utilized in sensor systems to describe physical properties of different objects. For medical applications it has been used to measure stiffness variations due to various patho-physiological conditions. In this study the sensor's ability to measure the stiffness of prostate tissue, from two excised prostatectomy specimens in vitro, was analysed. The specimens were also subjected to morphometric measurements, and the sensor parameter was compared with the morphology of the tissue with linear regression. In the probe impression interval 0.5-1.7 mm, the maximum R(2) > or = 0.60 (p < 0.05, n = 75). An increase in the proportion of prostate stones (corpora amylacea), stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Cancer and stroma had the greatest effect on the measured stiffness. The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed. Tissue sections deeper in the tissue were assigned a lower mathematical weighting than sections closer to the sensor probe. It is concluded that cancer increases the measured stiffness as compared with healthy glandular tissue, but areas with predominantly stroma or many stones could be more difficult to differ from cancer.
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| 15. |
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| 16. |
- Jalkanen, Ville, 1978-, et al.
(författare)
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Spatial variations in prostate tissue histology as measured by a tactile resonance sensor
- 2007
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Ingår i: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 28:10, s. 1267-81
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, tactile sensors based on piezoelectric resonance sensor technology have been used for medical diagnosis where the sensor's stiffness-measuring properties can reflect tissue pathology. The change in the frequency of the resonating system and the change in force when contact is made with tissue are used as a stiffness parameter. Earlier stiffness measurements of prostate tissue in vitro demonstrate variations related to tissue composition. In this study, measured stiffness from two human prostate specimens was compared to histological composition of prostate tissue below and around the measurement points. Tissue stiffness was measured with the resonance sensor system. Tissue composition was measured at four different depths in the tissue specimen using a microscopic-image-based morphometrical method. With this method, the proportion of tissue types was determined at the points of intersections in a circular grid on the images representing each measurement point. Numerical values were used for weighting the tissue proportions at different depths in the tissue specimen. For an impression depth of 1.0 mm, the sensing depth in this study was estimated to be 3.5-5.5 mm. Stiffness variations due to horizontal tissue variations were investigated by studying the dependence of the size of the circular grid area relative to the contact area of the sensor tip. The sensing area (grid radius) was estimated to be larger than the contact area (contact radius) between the sensor tip and the tissue. Thus, the sensor tip registers spatial variations in prostate tissue histology, both directly below and lateral to the tip itself. These findings indicate that tumours around the sensor tip could be detected, which in turn supports the idea of a future resonance-sensor-based clinical device for detecting tumours and for guiding biopsies.
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| 17. |
- Jonsson, Ulf G., 1950-, et al.
(författare)
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A FEM-Based Method Using Harmonic Overtones to Determine the Effective Elastic, Dielectric, and Piezoelectric Parameters of Freely Vibrating Thick Piezoelectric Disks
- 2013
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - New York : IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society. - 0885-3010 .- 1525-8955. ; 60:1, s. 243-255
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Tidskriftsartikel (refereegranskat)abstract
- To gain an understanding of the electroelasticproperties of tactile piezoelectric sensors used in the characterizationof soft tissue, the frequency-dependent electric impedanceresponse of thick piezoelectric disks has been calculatedusing finite element modeling. To fit the calculated to the measuredresponse, a new method was developed using harmonicovertones for tuning of the calculated effective elastic, piezoelectric,and dielectric parameters. To validate the results, theimpedance responses of 10 piezoelectric disks with diameterto-thickness ratios of 20, 6, and 2 have been measured from10 kHz to 5 MHz. A two-dimensional, general purpose finiteelement partial differential equation solver with adaptive meshingcapability run in the frequency-stepped mode, was used.The equations and boundary conditions used by the solver arepresented. Calculated and measured impedance responses arepresented, and resonance frequencies have been compared indetail. The comparison shows excellent agreement, with averagerelative differences in frequency of 0.27%, 0.19%, and0.54% for the samples with diameter-to-thickness ratios of 20,6, and 2, respectively. The method of tuning the effective elastic,piezoelectric, and dielectric parameters is an importantstep toward a finite element model that describes the propertiesof tactile sensors in detail.
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| 18. |
- Jonsson, Ulf G, 1950-
(författare)
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Detecting Inclusions in a Silicone Rubber Phantom Using Standing Lamb Waves and Multiple Frequency Footprints
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The thesis deals with one major question: is it possible, using one piezoelectric sensor/vibrator, to detect a hard inclusion in a silicone rubber phantom? The question was approached with an open mind and the task was subdivided into three clearly identifiable parts: characterization of the piezoelectric sensor/vibrator (paper I), creating a model of the visco-elastic properties of a tissue-like material (phantom) in contact with the sensor/vibrator (paper II), and to detect the presence of a hard inclusion in the phantom (paper III). All vibrations of the sensor/vibrator and phantom was modeled using a finite element method (FEM). To minimize the computational time and to maximize the FEM model's ability to correctly reproduce the vibrations, a two-dimensional model system consisting of a cylindrical piezoelectric sensor/vibrator, emitting radial elastic waves in to a cylindrical disk-shaped phantom, was chosen. The piezoelectric sensor/vibrator was characterized using a parameter tuning procedure using harmonic overtones. The procedure enables tuning of the electro-elastic parameters of the sensor/vibrator so that the measured and calculated impedance frequency responses match. Silicone rubber was chosen as a phantom to mimic soft tissue. The properties of the phantom was modeled using a fractional derivative visco-elastic model. The hyperelastic effect at the first radial resonance of the sensor vibrator was corrected for by a compensating function. The high frequency complex visco-elastic modulus of the silicone rubber was determined using the transitions of standing Lamb waves in the phantom. The presence of a ring-shaped inclusion in the phantom, of polyamide, was detected using the change of the transitional Lamb wave patterns in the phantom. The tuning of the PZT5A1 sensor/vibrator parameters yielded a match between the calculated and the measured impedance spectra better than 0.54%. The average, complex, elastic modulus of three silicone rubber, Silgel 612, samples were: (0.97 + 0.009i) GPa at 100 kHz and (0.97 + 0.005i) GPa at 250 kHz. The presence of a polyamide inclusion, PA6GPE, was detected in the phantom using multiple frequency footprints.
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| 19. |
- Jonsson, Ulf G, et al.
(författare)
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Modeling the high-frequency complex modulus of a silicone rubber using standing lamb waves and an inverse finite element method
- 2014
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - : IEEE Press. - 0885-3010 .- 1525-8955. ; 61:12, s. 2106-2120
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Tidskriftsartikel (refereegranskat)abstract
- To gain an understanding of the high-frequency elastic properties of silicone rubber, a finite element model of a cylindrical piezoelectric element, in contact with a silicone rubber disk, was constructed. The frequency dependent elastic modulus of the silicone rubber was modeled by a four parameter fractional derivative viscoelastic model in the 100 kHz to 250 kHz frequency range. The calculations were carried out in the range of the first radial resonance frequency of the sensor. At the resonance, the hyperelastic effect of the silicone rubber was modeled by a hyperelastic compensating function. The calculated response was matched to the measured response by using the transitional peaks in the impedance spectrum that originates from the switching of standing Lamb wave modes in the silicone rubber. To validate the results, the impedance responses of three 5 mm thick silicone rubber disks, with different radial lengths, were measured. The calculated and measured transitional frequencies have been compared in detail. The comparison showed very good agreement, with average relative differences of 0.7 %, 0.6 %, and 0.7 % for the silicone rubber samples with radial lengths of 38.0 mm, 21.4 mm, and 11.0 mm, respectively. The average, complex, elastic modulus of the samples were: (0.97 + 0.009i) GPa at 100 kHz and (0.97 + 0.005i) GPa at 250 kHz.
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| 20. |
- Jonsson, Ulf G., et al.
(författare)
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Using a look-up table technique and finite element calculations for quick detection of stiff inclusions in silicone rubber
- 2020
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Ingår i: Engineering computations. - : Emerald Group Publishing Limited. - 0264-4401 .- 1758-7077. ; 37:6, s. 2137-2153
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: The aim of the study was to show that a new method, using a look-up table technique, can be used to detect the presence and position of an inclusion embedded in a tissue-like material. Due to the time-consuming nature of the finite element (FE) method or FEM, real-time applications involving FEM as part of a control loop, are traditionally limited to slowly varying systems. By using a simplified two-dimensional FE model and a look-up table, we show by simulations and experiments that it is possible to achieve reasonable computational times in a tactile resonance sensor application.Design/methodology/approach: A piezoelectric disk was placed in the center of a silicone rubber disk (SRD) with viscoelastic properties, where it acted as both sensor and actuator and dissipated radial acoustic waves into the silicone. The look-up table was constructed by calculating the radial Lamb wave transition frequencies in the impedance frequency response of the sensor while varying the position of an inclusion. A position-matching algorithm was developed that matched measured and calculated Lamb wave transitions and thereby identified the presence and position of an inclusion.Findings: In an experiment, the position of a hard inclusion was determined by measuring the Lamb transition frequencies of the first radial resonance in two SRDs. The result of the matching algorithm for Disk 1 was that the matched position was less than 3% from the expected value. For Disk 2, the matching algorithm erroneously reported two false positions before reporting a position that was less than 5% from the expected value. An explanation for this discrepancy is presented. In a verifying experiment, the algorithm identified the condition with no inclusion present.Originality/value: The approach outlined in this work, adds to the prospect of developing time-sensitive diagnostic instruments. This approach has the potential to provide a powerful technique to quickly present spatial information on detected tumors.
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| 21. |
- Jonsson, Ulf G, et al.
(författare)
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Using Standing Lamb waves and the Finite Element Method to Detect Hard Inclusions in Silicone Rubber Disks
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The presence of an inclusion in a cylindrical silicone rubber disk is determined using FEM, standing Lamb waves, and an algorithm using multiple frequency footprints. Radial elastic waves are emitted into the disk by a cylindrical piezoelectric sensor placed in the center of the disk. The visco-elastic properties of the silicone rubber disk is modeled by a fractional derivative model and the hyperelastic effect at the radial resonance frequency was compensated for. Using the finite element model, the Lamb wave transition frequencies in the impedance frequency response of the sensor was calculated for a specified position of the inclusion. The set of frequencies was named the footprint for that position. The position of the inclusion was varied between 0.05 to 0.95, with a step of 0.01, of the radial length of the silicone rubber disk. For each position, a footprint was calculated. The footprints,s, with corresponding positions, were stored in a database. A positioning algorithm was developed that could match an unknown footprint to a footprint in the database. A self-test of the algorithm showed that the correct position was found for 94% of the tested positions. The results of the positioning algorithm was that the presence of the inclusions were detected, and that the positions of the inclusions at 0.38 and 0.63 were estimated by the positioning algorithm as: 0.45 and 0.74, with relative errors +18% and +17% respectively. The positions are given as the ratio of the radius of the inclusion to the silicone rubber disk radius.
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| 22. |
- Lindahl, Olof A, et al.
(författare)
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A tactile resonance sensor for prostate cancer detection – evaluation on human prostate tissue
- 2021
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Ingår i: Biomedical Engineering & Physics Express. - : Institute of Physics (IOP). - 2057-1976. ; 7:2
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Tidskriftsartikel (refereegranskat)abstract
- Prostate cancer surgery risks erectile problems and incontinence for the patient. An instrument for guiding surgeons to avoid nerve bundle damage and ensure complete cancer removal is desirable. We present a tactile resonance sensor made of PZT ceramics, mounted in a 3D motorized translation stage for scanning and measuring tissue stiffness for detecting cancer in human prostate. The sensor may be used during surgery for guidance, scanning the prostate surface for the presence of cancer, indicating migration of cancer cells into surrounding tissue. Ten fresh prostates, obtained from patients undergoing prostate cancer surgery, were cut into 0.5 cm thick slices. Each slice was measured for tissue stiffness at about 25 different sites and compared to histology for validation cancer prediction by stiffness. The statistical analysis was based on a total of 148 sites with non-cancer and 40 sites with cancer. Using a generalized linear mixed model (GLMM), the stiffness data predicted cancer with an area under the curve of 0.74, after correcting for overfitting using bootstrap validation. Mean prostate stiffness on the logarithmic scale (p = 0.015) and standardized Z-scores (p = 0.025) were both significant predictors of cancer. This study concludes that stiffness measured by the tactile resonance sensor is a significant predictor of prostate cancer with potential for future development towards a clinical instrument for surgical guidance.
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| 23. |
- Lindahl, Olof A, et al.
(författare)
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Biomedical engineering research improves the health care industry
- 2014
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Ingår i: XIII Mediterranean Conference on Medical and Biological Engineering and Computing 2013. - Cham : Springer. - 9783319008455 - 9783319008462 ; , s. 1124-1126
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Konferensbidrag (refereegranskat)abstract
- The health care industry is dependent on new innovations for its survival and expansion. Health care innovations are also important for improving patient care. Through activities at the centre for biomedical engineering and physics (CMTF) we have generated growth both in academia at the universities and in the industry in northern Sweden. Fruitful cooperation was generated between 26 research projects and about 15 established companies in the field of biomedical engineering. The established researcher-owned company for business development of the research results from the CMTF, CMTF Business Development Co Ltd, has so far launched three spin-off companies and has 10 new business leads to develop. The activities have also increased the interest for commercialization and entrepreneurship among the scientists in the centre. So far a total of nine spin-off companies have resulted from the CMTF-research since the year 2000 that has improved the health care market in northern Sweden. © Springer International Publishing Switzerland 2014.
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| 24. |
- Lindahl, Olof A
(författare)
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From biomedical research to viable products on the health care market : a North Sweden model called CMTF
- 2009
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Ingår i: IFMBE Proceedings. - Berlin, Heidelberg : Springer. - 9783642038921 - 9783642038938 ; , s. 127-130, s. 127-130
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Konferensbidrag (refereegranskat)abstract
- A centre for research in Biomedical engineering and physics (CMTF) has been built up in Northern Sweden. The CMTF has resulted in increased growth of the biomedical engineering activities both in academia and in the industry in Northern Sweden. Fore example six new companies have resulted from the research. Cooperation was built up between the CMTF and 15 established companies. A research company for business development of the research results from the centre has been established and is owned by the project managers in the centre. The company is called CMTF Business Development Co Ltd and it has also increased the interest for business development questions among the scientists in the centre, i.e. encouraged entrepreneurship.
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| 25. |
- Lindahl, Olof A, et al.
(författare)
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Prostate cancer detection ex vivo combining Raman spectroscopy and tactile resonance technology
- 2018
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Ingår i: EMBEC & NBC 2017. - Singapore : SPRINGER-VERLAG SINGAPORE PTE LTD. - 9789811051210 - 9789811051227 ; , s. 193-196, s. 193-196
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Konferensbidrag (refereegranskat)abstract
- Prostate cancer is the most common cancer for men in the western world. The most prevalent curative treatment is radical prostatectomy. However, prostate surgery can give unwanted side effects and there is a need for an instrument that can provide decision support to the surgeon during surgery on the presence of cancer cells in the surgical margin. A dual modality probe, combining Raman spectroscopy and tactile resonance technology, has been used for detecting cancer in fresh human prostate tissue. The tactile resonance modality measures the tissue stiffness and Raman spectroscopy depicts the molecular content in tissue, both related to cancer. After ethical approval, the study investigated the potential of the dual-modality probe by testing its ability to differentiate between normal and cancerous prostate tissue ex vivo. It also investigated the minimal amount of measurement points needed to securely detect cancer on the surface of prostate tissue. Measurements on three prostate tissue slices show that the tactile resonance modality measuring stiffness was able to detect differences between normal and cancerous tissue on a significant level of 90%, but the sample size was too low to draw any firm conclusions. It was also suggested from the study results that the high wavenumber region in the Raman spectrum can give valuable information about cancer in prostate tissue. A number of 24 measurement points were enough for detecting cancer in prostate slices in this study. It can be suggested from this study that combining these two sensor modalities is promising for accurate detection of prostate cancer that is needed during prostate surgery, but more measurements including more prostates must be performed before the full value of the study result can be established.
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| 26. |
- Lindahl, Olof A., et al.
(författare)
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Prostate cancer detection using a combination of Raman spectroscopy and stiffness sensing
- 2014
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Ingår i: 1st Global Conference on Biomedical Engineering & 9th Asian-Pacific Conference on Medical and Biological Engineering. - New York : Encyclopedia of Global Archaeology/Springer Verlag. - 9783319122625 - 9783319122625 - 9783319122618 ; , s. 267-270
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Konferensbidrag (refereegranskat)abstract
- Prostate cancer (PCa) is the most common cancer form for men in Europe. A sensor system combining Raman spectroscopy and stiffness sensing with a resonance sensor has recently been developed by us for prostate cancer detection. In this study the sensor system has been used for measurements on two slices of fresh human prostate tissue. The stiffness sensor could detect locations slices with significantly different stiffness contrasts (p < 0.05). Raman spectroscopic measurements could be performed with the dual-modality probe for tissue classification. The findings are important for the continued development of a combination probe for prostate cancer detection.
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| 27. |
- Lindahl, Olof, et al.
(författare)
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Grip strength of the human hand : measurements on normal subjects with a new hand strength analysis system (Hastras)
- 1994
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Ingår i: Journal of Medical Engineering & Technology. - : Informa UK Limited. - 0309-1902 .- 1464-522X. ; 18:3, s. 101-103
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Tidskriftsartikel (refereegranskat)abstract
- This study describes a method of acquiring data from healthy and non-injured men that can be used as reference data when measuring the grip strength of the human hand using newly developed, PC-based hand strength analysis equipment--'Hastras'. Hastras can be used for continuous measurement and recording of force when the subject grips a sensor with maximum power. Computerized analysis of the force signal gives information about maximum force, fatigue, area and rise (force/s). The statistical analysis of the measurements on 81 subjects are consistent with earlier published data from other hand strength equipment. It is concluded that Hastras gives easy processing and storage of data, and also a detailed analysis of grip function.
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| 28. |
- Lindahl, R, et al.
(författare)
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Determination of morpholine in air by derivatisation with 1-naphthylisothiocyanate and HPLC analysis
- 2001
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Ingår i: The Analyst. - : Royal Society of Chemistry. - 0003-2654 .- 1364-5528. ; 126:2, s. 152-154
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Tidskriftsartikel (refereegranskat)abstract
- A method for the determination of morpholine in air was developed. Samples were collected with adsorbent tubes containing XAD-2 resin coated with 1-naphthylisothiocyanate (NIT). The thiourea derivative formed was subsequently desorbed with acetonitrile and analysed by HPLC with UV detection. The recovery after gas phase spiking with morpholine (2.2-1570 micrograms) was 91% (86-100%) with a relative standard deviation of 5.5%. No effect on recovery from relative humidity or amount of morpholine was seen. The lowest level tested corresponded to 7 mg m-3 (1/10 threshold limit value) for a 15 min sampling period with a sampling rate of 20 ml min-1. Exposed NIT-coated XAD-2 tubes were stable at room temperature for at least 2 weeks.
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| 29. |
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| 30. |
- Morel, Chantal M., et al.
(författare)
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Industry incentives and antibiotic resistance : an introduction to the antibiotic susceptibility bonus
- 2020
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Ingår i: Journal of antibiotics (Tokyo. 1968). - : NATURE PUBLISHING GROUP. - 0021-8820 .- 1881-1469. ; 73:7, s. 421-428
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Forskningsöversikt (refereegranskat)abstract
- The scarcity of novel antibiotic compounds in a time of increasing resistance rates has begun to ring alarm bells at the highest echelons of government. Large new financial incentives to accelerate antibiotic research and development, such as market entry rewards (MERs), are being considered. However, there is little focus on how to sustain the efficacy of new, promising antibiotics reaching the market. Currently, inappropriate use of antibiotics is commonplace, which has accelerated resistance development. In an attempt to halt this trend, antibiotic stewardship policies are being implemented in many resource-rich settings. Unfortunately, this has not yet had an impact on the amount of antibiotics being prescribed globally. One important hurdle is misalignment of incentives. While governments and health services are incentivized to promote prudent use of this common good, pharmaceutical companies are incentivized to increase volume of sales to maximize profits. This problem must be addressed or else the major efforts going into developing new antibiotics will be in vain. In this paper we outline an approach to realign the incentives of pharmaceutical companies with wider antibiotic conservation efforts by making a staged bonus a component of an MER for antibiotic developers when resistance to their drug remains low over time. This bonus could address the lack of stewardship focus in any innovation-geared incentive.
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| 31. |
- Murayama, Yoshinobu, et al.
(författare)
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Sensitivity improvements of a resonance-based tactile sensor.
- 2017
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Ingår i: Journal of Medical Engineering & Technology. - : Informa UK Limited. - 0309-1902 .- 1464-522X. ; 41:2, s. 131-140
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Tidskriftsartikel (refereegranskat)abstract
- Resonance-based contact-impedance measurement refers to the application of resonance sensors based on the measurement of the changes in the resonance curve of an ultrasonic resonator in contact with a surface. The advantage of the resonance sensor is that it is very sensitive to small changes in the contact impedance. A sensitive micro tactile sensor (MTS) was developed, which measured the elasticity of soft living tissues at the single-cell level. In the present paper, we studied the method of improving the touch and stiffness sensitivity of the MTS. First, the dependence of touch sensitivity in relation to the resonator length was studied by calculating the sensitivity coefficient at each length ranging from 9 to 40 mm. The highest touch sensitivity was obtained with a 30-mm-long glass needle driven at a resonance frequency of 100 kHz. Next, the numerical calculation of contact impedance showed that the highest stiffness sensitivity was achieved when the driving frequency was 100 kHz and the contact-tip diameter of the MTS was 10 μm. The theoretical model was then confirmed experimentally using a phase-locked-loop-based digital feedback oscillation circuit. It was found that the developed MTS, whose resonant frequency was 97.030 kHz, performed with the highest sensitivity of 53.2 × 10(6) Hz/N at the driving frequency of 97.986 kHz, i.e. the highest sensitivity was achieved at 956 Hz above the resonant frequency.
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| 32. |
- Nyberg, Morgan, et al.
(författare)
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A combined tactile and Raman probe for tissue characterization - Design considerations
- 2012
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Ingår i: Measurement Science and Technology. - : IOP Publishing. - 0957-0233 .- 1361-6501. ; 23:6
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Tidskriftsartikel (refereegranskat)abstract
- Histopathology is the golden standard for cancer diagnosis and involves the characterization of tissue components. It is labour intensive and time consuming. We have earlier proposed a combined fibre-optic near-infrared Raman spectroscopy (NIR-RS) and tactile resonance method (TRM) probe for detecting positive surgical margins as a complement to interoperative histopathology. The aims of this study were to investigate the effects of attaching an RS probe inside a cylindrical TRM sensor and to investigate how laser-induced heating of the fibre-optic NIR-RS affected the temperature of the RS probe tip and an encasing TRM sensor. In addition, the possibility to perform fibre-optic NIR-RS in a well-lit environment was investigated. A small amount of rubber latex was preferable for attaching the thin RS probe inside the TRM sensor. The temperature rise of the TRM sensor due to a fibre-optic NIR-RS at 270 mW during 20 s was less than 2 degrees C. Fibre-optic NIR-RS was feasible in a dimmed bright environment using a small light shield and automatic subtraction of a pre-recorded contaminant spectrum. The results are promising for a combined probe for tissue characterization.
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| 33. |
- Nyberg, Morgan, 1971-, et al.
(författare)
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Dual-modality probe intended for prostate cancer detection combining Raman spectroscopy and tactile resonance technology—discrimination of normal human prostate tissues ex vivo
- 2015
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Ingår i: Journal of Medical Engineering & Technology. - : Taylor & Francis. - 0309-1902 .- 1464-522X. ; 39:3, s. 198-207
-
Tidskriftsartikel (refereegranskat)abstract
- Prostate cancer is the most common cancer for men in the western world. For the first time, a dual-modality probe, combining Raman spectroscopy and tactile resonance technology, has been used for assessment of fresh human prostate tissue. The study investigates the potential of the dual-modality probe by testing its ability to differentiate prostate tissue types ex vivo. Measurements on four prostates show that the tactile resonance modality was able to discriminate soft epithelial tissue and stiff stroma (p<0.05). The Raman spectra exhibited a strong fluorescent background at the current experimental settings. However, stroma could be discerned from epithelia by integrating the value of the spectral background. Combining both parameters by a stepwise analysis resulted in 100% sensitivity and 91% specificity. Although no cancer tissue was analysed, the results are promising for further development of the instrument and method for discriminating prostate tissues and cancer.
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| 34. |
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| 35. |
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| 36. |
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| 37. |
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| 38. |
- Åstrand, Anders, et al.
(författare)
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Contact angle and indentation velocity dependency for a resonance sensor : Evaluation on soft tissue silicone models
- 2013
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Ingår i: Journal of Medical Engineering & Technology. - : Informa Healthcare. - 0309-1902 .- 1464-522X. ; 37:3, s. 185-196
-
Tidskriftsartikel (refereegranskat)abstract
- Human tissue stiffness can vary due to different tissue conditions such as cancer tumours. Earlier studies show that stiffness may be detected with a resonance sensor that measures frequency shift and contact force at application. Through the frequency shift and the contact force, a tissue stiffness parameter can be derived. This study evaluated how the probe application angle and indentation velocity affected the results and determined the maximum parameter errors. The evaluation was made on flat silicone discs with specified hardness. The frequency shift, the force and the stiffness parameter all varied with contact angle and indentation velocity. A contact angle of ≤10° was acceptable for reliable measurements. A low indentation velocity was recommended. The maximum errors for the system were <1.1% of the measured values. It was concluded that contact angle and indentation velocity have to be considered in the clinical setting. The angular dependency is especially important in clinical use for studying stiffness of human soft tissue, e.g. in prostate cancer diagnosis.
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| 39. |
- Åstrand, Anders P.
(författare)
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A flexible resonance sensor system for detection of cancer tissue : evaluation on silicon
- 2012
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The most common form of cancer among men in Europe and the US is prostate cancer. When a radical prostatectomy has been found necessary, it is of interest to examine the prostate, as tumour tissue on the capsule might indicate that the cancer has metastased. This is commonly done by a microscope-based morphometric investigation. Tumour tissue is normally stiffer than healthy tissue. Sensors based on piezoelectric resonance technology have been introduced into the medical field during the last decade. By studying the change in resonance frequency when a sensor comes into contact with a material, conclusions can be drawn about the material.A new and flexible measurement system using a piezoelectric resonance sensor has been evaluated. Three translation stages, two for horizontal movements and one for vertical movement, with stepper motors are controlled from a PC. A piezoelectric resonance element and a force sensor are integrated into a sensor head that is mounted on the vertical translation stage. The piezoelectric element is connected to a feed-back circuit and resonating at its resonance frequency until it comes into contact with a material, when a frequency shift can be observed. The force sensor is used to measure the applied force between the sensor and the material. These two parameters are combined into a third, called the stiffness parameter, which is important for stiffness evaluation. For measurements on objects with different geometries, the vertical translation stage can be aimed at a platform for flat objects or a fixture for spherical objects. The vertical translation stage is mounted on a manual rotational stage with which the contact angle between the sensor and the measured surface can be adjusted. The contact angles covered are between 0° and 35° from a line perpendicular to the surface of the measured object. The measured objects used were made from silicones of different stiffness and in the shape of flat discs and spheres. The indentation velocity of the sensor can be set at 1 mm/s to 5 mm/s. In the three papers that are the base for this licentiate thesis, we have investigated the dependence of the frequency shift, the applied force and the stiffness parameter on the contact angle, and the indentation velocity at different impression depths. The maximum error for the measurement system has also been determined.The results of the measurements indicate that great care must be taken when aiming the sensor against the surface of the point where the measurements are to be performed. Deviations in contact angle of more than iv±10° from a line perpendicular to the surface will result in an underestimation of the frequency shift, meaning that the tissue will be regarded as stiffer than it really is. This result is important as the flat silicone models have a very even surface, which makes a controlled contact angle possible. Biological tissue can have a rough and uneven surface, which can lead to unintentional deviations in the contact angle. The magnitude of the stiffness parameter is favoured by a high indentation velocity compared to a low.The evaluation of this measurement system has shown that it is possible to distinguish between soft and stiff silicone models, which have been used in this initial phase of the study. A new feature in this measurement system is the fixture that makes measurements on spherical objects possible and the possibility to vary the angle of contact. This is promising for future studies and measurements on whole prostate in vitro. A future application for this measurement system is to aid surgeons performing radical prostatectomy in the search for tumour tissue on the capsule of the prostate, as the presence of tumour tissue can indicate that the cancer has spread to the surrounding tissue.
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| 40. |
- Åstrand, Anders P., et al.
(författare)
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A flexible sensor system using resonance technology for soft tissue stiffness measurements : evaluation on silicone
- 2011
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Ingår i: 15TH NORDIC-BALTIC CONFERENCE ON BIOMEDICAL ENGINEERING AND MEDICAL PHYSICS (NBC 2011). - Aalborg : Springer. - 9783642216824 ; , s. 21-24
-
Konferensbidrag (refereegranskat)abstract
- One of the most common forms of cancer amongmen in Europe and the United States is prostate cancer. Thecancerous tissue is less soft, and has different biomechanicalproperties compared to healthy tissue. It has been shown thattactile sensors can be used to distinguish this difference. If apiezoelectric sensor is set to oscillate at its resonance frequencythrough a feed back circuit, a frequency shift is observed whenthe sensor comes in contact with a surface. This shift can becorrelated to the stiffness of the tissue. A flexible instrumenthas been developed, with which it is possible to scan both flatand spherical bodies and where the sensor can be tilted to havedifferent contact angles. Measurements performed in thisstudy on flat silicone discs of different stiffness showed arelationship between both the frequency shift and theimpression depth for the different silicone discs, when aconstant force was applied. The results are promising forfuture studies on silicone with different geometries and finallyon prostate tissue to complete the evaluation.
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| 41. |
- Åstrand, Anders P, 1961-
(författare)
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A Tactile Resonance Sensor System for Detection of Prostate Cancer ex vivo : Design and Evaluation on Tissue Models and Human Prostate
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Background The most common form of cancer among males in Europe and the USA is prostate cancer, PCa. Surgical removal of the prostate is the most common form of curative treatment. PCa can be suspected by a blood test for a specific prostate antigen, a PSA-test, and a digital rectal examination, DRE where the physician palpates the prostate through the rectum. Stiff nodules that can be detected during the DRE, and elevated levels of PSA are indications for PCa, and a reason for further examination. Biopsies are taken from the prostate by guidance of a transrectal ultrasound. Superficial cancer tumours can indicate that the cancer has spread to other parts of the body. Tactile resonance sensors can be used to detect areas of different stiffness in soft tissue. Healthy prostate tissue is usually of different stiffness compared to tissue with PCa.AimThe general aim of this doctoral thesis was to design and evaluate a flexible tactile resonance sensor system (TRSS) for detection of cancer in soft human tissue, specifically prostate cancer. The ability to detect cancer tumours located under the surface was evaluated through measurements on tissue phantoms such as silicone and biological tissues. Finally measurements on resected whole prostate glands were made for the detection of cancer tumours.Methods The sensor principle was based on an oscillating piezoelectric element that was indented into the soft tissue. The measured parameters were the change in resonance frequency, Δf, and the contact force F during indentation. From these, a specific stiffness parameter was obtained. The overall accuracy of the TRSS was obtained and the performance of the TRSS was also evaluated on tissue models made of silicone, biological tissue and resected whole human prostates in order to detect presence of PCa. Prostate glands are generally spherical and a special rotatable sample holder was included in the TRSS. Spherically shaped objects and uneven surfaces call for special attention to the contact angle between the sensor-tip and the measured surface, which has been evaluated. The indentation velocity and the depth sensitivity of the sensor were evaluated as well as the effect on the measurements caused by the force with which spherical samples were held in place in the sample holder. Measurements were made on silicone models and biological tissue of chicken and pork muscles, with embedded stiff silicone nodules, both on flat and spherical shaped samples. Finally, measurements were made on two excised whole human prostates.ResultsA contact angle deviating ≤ 10° from the perpendicular of the surface of the measured object was acceptable for reliable measurements of the stiffness parameter. The sensor could detect stiff nodules ≤ 4 mm under the surface with a small indentation depth of 0.4 to 0.8 mm.Measurements on the surface of resected human prostate glands showed that the TRSS could detect stiff areas (p < 0.05), which were confirmed by histopathological evaluation to be cancer tumours on, and under the surface.Conclusions A flexible resonance sensor system was designed and evaluated on soft tissue models as well as resected whole prostate glands. Evaluations on the tissue models showed that the TRSS can detect stiffer volumes hidden below the surface on both flat and spherical samples. The measurements on resected human prostate glands showed that PCa could be detected both on and under the surface of the gland. Thus the TRSS provides a promising instrument aimed for stiffness measurements of soft human tissue that could contribute to a future quantitative palpation method with the purpose of diagnosing cancer.
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| 42. |
- Åstrand, Anders P., et al.
(författare)
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Initial measurements on whole human prostate ex vivo with a tactile resonance sensor in order to detect prostate cancer
- 2015
-
Ingår i: 16th Nordic-Baltic Conference on Biomedical Engineering. - Cham : Springer. - 9783319129662 - 9783319129679 ; , s. 120-123
-
Konferensbidrag (refereegranskat)abstract
- Prostate cancer (PCa) is the most common form of cancer among the male population in Europe and the USA. PCa can be suspected by a blood test for a specific prostate antigen, a PSA-test, followed by a digital rectal examination (DRE). The objective with the DRE is to investigate the presence of stiff nodules on the prostate. Stiff nodules can indicate PCa and biopsies are taken from the suspicious parts of the prostate using guidance of a transrectal ultrasound. Microscopic evaluation of the biopsies is used for final diagnosis. Superficial tumor growth on, and beneath the surface of the gland is of special interest as it suggests that the cancer has spread to other parts of the body.Tactile resonance sensors can be used to distinguish between areas of different stiffness in soft tissue. The aim was to detect tumors on, and beneath the surface of a whole human prostate ex vivo.A tactile resonance sensor system (TRSS) based on a piezoelectric resonance sensor and a force sensor has been used to detect areas with increased stiffness in soft tissue. The TRSS has a rotatable sample holder for measurements on spherical shaped samples. Stiffness measurements were made on samples of porcine muscle tissue with embedded stiff silicone nodules placed under the surface. Further measurements were made on a resected whole human prostate with PCa.The results showed that through the measured stiffness parameter, the stiff silicone nodules placed down to 4 mm under the surface could be detected. The measurements on the prostate showed that elevated values of the stiffness parameter correlated (p < 0.05) with areas in the anterior of the prostate where cancer tumors were detected by histopathological evaluation. The tumors were significantly stiffer than the healthy tissue in the dorsal region.The results are promising for further development of a clinically useful instrument to detect superficial PCa.
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| 43. |
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| 44. |
- Åstrand, Anders, et al.
(författare)
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Stiffness measurements on spherical surfaces of prostate models using a resonance sensor
- 2013
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Ingår i: World Congress on Medical Physics and Biomedical Engineering May 26-31, 2012, Beijing, China. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783642293047 - 9783642293054 ; , s. 1401-1404
-
Konferensbidrag (refereegranskat)abstract
- Prostate cancer is one of the most common formsof cancer among men in Europe and the United States.Piezoelectric resonance sensors can be used in medicalresearch for measurements of stiffness of human tissue.Cancer tissue is usually stiffer and has different biomechanicalproperties compared to healthy tissue. The frequency shiftobserved when a piezoelectric resonance sensor comes intocontact with a tissue surface has been suggested to correlatewith the stiffness variations, e.g. due to cancer. An instrumenthas been developed, with which it is possible to scan flat andspherical objects and where the sensor can be tilted fordifferent contact angles. Measurements performed in thisstudy on spherical tissue models made of silicone, showed theimportance of keeping the contact angle perpendicular to thesurface of the sphere. The results are promising for futurestudies on prostate tissue to complete the evaluation of theinstrument.
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