Change search
Refine search result
12345 1 - 50 of 203
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Alrifaiy, Ahmed
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    A gastight microfluidic system combined with optical tweezers and optical spectroscopy for electrophysiological investigations of single biological cells2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Stroke affects around 20 million people around the world every year. Clinically, stroke is a result of brain damage due to the shortage of oxygen delivered to the nerve cells. To minimize suffering and costs related to the disease, extensive research is performed on different levels. The focus of our research is to achieve fundamental understanding on how the lack of oxygen in brain tissue activates intrinsic biomolecular defense mechanisms that may reduce brain damage. More knowledge may hopefully lead to new therapeutic and preventive strategies on the molecular level for individuals in the risk zone for stroke or those who have just suffered a stroke. The area of study is based on the discovery of a hemoprotein called neuroglobin (Ngb), which is found in various regions in the brain, in the islets of Langerhans, and in the retina. Several studies have shown that Ngb seems to have a protective function against hypoxia-related damage. However, until now, it has not been understood how Ngb affects the nerve system and protects neurons from damage. The well-established patch-clamp technique is routinely used to measure and analyze the electrophysiological activity of individual biological cells. To perform accurate patchclamp experiments, it is important to create well-controlled physiological conditions, i.e. different oxygen levels and fast changes of nutrients and other biochemical substances. A promising approach is to apply lab-on-a-chip technologies combined with optical manipulation techniques. These give optimal control over fast changing environmental conditions and enable multiple readouts. The conventional open patch-clamp configuration cannot provide adequate control of the oxygen content. Therefore, it was substituted by a gas-tight multifunctional microfluidic system, a lab-on-a-chip, with an integrated patch-clamp micropipette. The system was combined with optical tweezers and optical spectroscopy. Laser tweezers were used to optically guide and steer single cells towards the fixed micropipette. Optical spectroscopy was used to investigate the biochemical composition of the sample. The designed, closed lab-on-a-chip acted as a multifunctional system for simultaneous electrophysiological and spectroscopic experiments with good control over the oxygen content in the liquid perifusing the cells. The system was tested in a series of experiments: optically trapped human red blood cells were steered to the fixed patch-clamp pipette within the microfluidic system. The oxygen content within the microfluidic channels was measured to 1 % compared to the usual 4-7 %. The trapping dynamics were monitored in real-time while the spectroscopic measurements were performed simultaneously to acquire absorption spectra of the trapped cell under varying environments. To measure the effect of the optical tweezers on the sample, neurons from rats in a Petri dish were optically trapped and steered towards the patch-clamp micropipette where electrophysiological investigations were performed. The optical tweezers had no effect on the electrophysiological measurements. Similar investigations within a closed microfluidic system were initiated and showed promising results for further developments of a complete lab-on-a-chip multifunctional system for reliable patch-clamp measurements. The future aim is to perform complete protocols of patch-clamp electrophysiological investigations while simultaneously monitoring the biochemical composition of the sample by optical spectroscopy. The straightforwardness and stability of the microfluidic chip have shown excellent potential to enable high volume production of scalable microchips for various biomedical applications. The subsequent ambition is to use this system as a mini laboratory that has benefits in cell sorting, patch-clamp, and fertilization experiments where the gaseous and the biochemical content is of importance. The long-term goal is to study the response of individual neurons and defense mechanisms under hypoxic conditions that may establish new ways to understand cell behavior related to Ngb for various diseases such as stroke, Alzheimer’s and Parkinson’s.

  • 2.
    Alrifaiy, Ahmed
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lab on a chip for electrophysiological measurements with control of the oxygen content: optical manipulation and spectroscopic analysis of biological cells2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Stroke affects nearly 20 million people around the world every year. Clinically, stroke is a result of brain damage due to the shortage of oxygen delivered to the nerve cells. To minimize suffering and costs related to the disease, extensive research is performed on different levels. The focus of our research is to achieve fundamental understanding on how the lack of oxygen in brain tissue activates intrinsic biomolecular defense mechanisms that may reduce brain damage. More knowledge may hopefully lead to new therapeutic and preventive strategies on the molecular level for individuals in the risk zone for stroke or those who have just suffered a stroke.The area of study is based on the discovery of a hemoprotein called neuroglobin (Ngb), which is found in various regions in the brain, in the islets of Langerhans, and in the retina. Several studies have shown that Ngb seems to have a protective function against hypoxia-related damage. However, until now, it has not been understood how Ngb affects the nerve system and protects neurons from damage.The well-established patch-clamp technique is routinely used to measure and analyze the electrophysiological activity of individual biological cells. To perform accurate patchclamp experiments, it is important to create well-controlled physiological conditions, i.e. different oxygen levels and fast changes of nutrients and other biochemical substances. A promising approach is to apply lab on a chip technologies combined with optical manipulation techniques. These give optimal control over fast changing environmental conditions and enable multiple readouts.The conventional open patch-clamp configuration cannot provide adequate control of the oxygen content. Therefore, the aim of the thesis was to design and test a multifunctional microfluidic system, lab on a chip (LOC), that can achieve normoxic, anoxic and hypoxic conditions. The conventional patch clamp configuration was substituted by a gas-tight LOC system with an integrated patch-clamp micropipette. The system was combined with optical tweezers, optical sensor and optical spectroscopy.Optical tweezers were used to trap and guide single cells through the LOC microchannels towards the fixed micropipette. Optical spectroscopy was essential to investigate the biochemical composition of the biological samples. The developed, gas-tight LOC acted as a multifunctional system for simultaneous electrophysiological and spectroscopic experiments with good control over the oxygen content in the liquid perifusing the cells. The system was tested in series of experiments: optically trapped cells (red blood cells from human and chicken and nerve cells) were steered to the fixed patch-clamp pipette within the LOC system. The oxygen content within the microfluidic channels was measured to ∼ 1% compared to the usual 4-7% found in open system. The trapping dynamics were monitored in real-time while the spectroscopic measurements were performed simultaneously to acquire absorption spectra of the trapped cell under varying environments. To measure the effect of the laser tweezers on the sample, neurons from rats in a Petri dish were optically trapped and steered towards the patch-clamp micropipette where electrophysiological investigations were performed. The optical tweezers had no effect on the electrophysiological measurements.The future aim is to perform complete protocols of patch-clamp electrophysiological investigations while simultaneously monitoring the biochemical composition of the sample by optical spectroscopy. The straightforwardness and stability of the microfluidic chip have shown excellent potential to be applied for various biomedical applications. The subsequent ambition is to use this system as a mini laboratory that has benefits in cell sorting, patch-clamp and fertilization experiments where the gaseous and the biochemical content is of importance.The long-term goal is to study the response of individual neurons and defense mechanisms under hypoxic conditions that may establish new ways to understand cell behavior related to Ngb for various diseases such as stroke, Alzheimer’s and Parkinson’s.

  • 3.
    Alrifaiy, Ahmed
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Bitaraf, Nazanin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Druzin, Michael
    Umeå universitet, Integrativ Medicinsk Biologi, Fysiologi.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Hypoxia on a chip: a novel approach for patch-clamp studies in a microfluidic system with full oxygen control2012In: World Congress on Medical Physics and Biomedical Engineering, May 26-31, 2012, Beijing, China / [ed] Mian Long, Berlin: Encyclopedia of Global Archaeology/Springer Verlag, 2012, p. 313-316Conference paper (Refereed)
    Abstract [en]

    Here a new approach to perform patch-clamp investigations under anoxic and normoxic conditions on nerve cells from Sprague Dawley rats is presented. A patch-clamp micropipette is integrated within a poly-methyl methacrylate (PMMA) based microchip giving optimal control over the oxygen content and the biochemical environment. Nerve cells were trapped by optical tweezers and steered towards the patch-clamp micropipette within the micro-channels. Several experiments were performed to show proof of principle. The oxygen content within the microfluidic chamber was measured to 0.5-1.5 %. The photo-induced effect of the optical tweezers on the nerve cells was investigated in an open Petri dish. The optical trapping did not influence measurements. The microfluidic system was further tested in patch-clamp experiments. This approach showed significant advantages regarding the tuning of the oxygen content and may be used in various electrophysiological investigations of single cells demanding optimal control of the surroundings.

  • 4.
    Alrifaiy, Ahmed
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Bitaraf, Nazanin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Druzin, Michael
    Umeå universitet, Integrativ Medicinsk Biologi, Fysiologi.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Patch-clamp measurements on a chip with full control over the oxygen content2012In: Journal of Biochips & Tissue Chips, ISSN 2153-0777, Vol. 2, no 1, p. 1-5Article in journal (Refereed)
  • 5.
    Alrifaiy, Ahmed
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Bitaraf, Nazanin
    Lindahl, Olof
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Development of microfluidic system and optical tweezers for electrophysiological investigations of an individual cell2010In: Optical Trapping and Optical Micromanipulation VII: 1 - 5 August 2010, San Diego, California, United States ; [part of SPIE optics + photonics] / [ed] Kishan Dholakia; Gabriel C. Spalding, Bellingham, Wash: SPIE - International Society for Optical Engineering, 2010Conference paper (Refereed)
    Abstract [en]

    We present a new approach of combining Lab-on-a-chip technologies with optical manipulation technique for accurate investigations in the field of cell biology. A general concept was to develop and combine different methods to perform advanced electrophysiological investigations of an individual living cell under optimal control of the surrounding environment. The conventional patch clamp technique was customized by modifying the open system with a gas-tight multifunctional microfluidics system and optical trapping technique (optical tweezers).The system offers possibilities to measure the electrical signaling and activity of the neuron under optimum conditions of hypoxia and anoxia while the oxygenation state is controlled optically by means of a spectroscopic technique. A cellbased microfluidics system with an integrated patch clamp pipette was developed successfully. Selectively, an individual neuron is manipulated within the microchannels of the microfluidic system under a sufficient control of the environment. Experiments were performed to manipulate single yeast cell and red blood cell (RBC) optically through the microfluidics system toward an integrated patch clamp pipette. An absorption spectrum of a single RCB was recorded which showed that laser light did not impinge on the spectroscopic spectrum of light. This is promising for further development of a complete lab-on-a-chip system for patch clamp measurements.

  • 6.
    Alrifaiy, Ahmed
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Bitaraf, Nazanin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ett mikroflödessystem för multipla undersökningar av enstaka biologiska celler under hypoxiska förhållanden2011Conference paper (Refereed)
    Abstract [sv]

    Introduktion: Syftet med studien är att studera enstaka nervcellers respons vid syrebrist i ett mikroflödessystem för att förstå nervcellens respons vid stroke. Målet med studien var att utveckla ett slutet mikroflödessystem som ger optimal kontroll av den omgivande miljön och samtidigt möjliggöra elektrofysiologiska undersökningar under kontrollerade syreförhållande. Material och metoder: Mikroflödescellen utvecklades för ett inverterat mikroskop, utrustad med en optisk pincett och optisk spektroskopi samt patch-clamp för elektrofysiologiska studier på en enstaka nervcell. Istället för att föra en pipett mot en cell i ett öppet system fångades en enskild cell optiskt i ett slutet mikroflödessystem och fördes mot en fixerad patch-clamp mikropipett. Cellen utsattes för olika syrehalter och övervakades av ett UV-Vis spektroskop medan cellens elektrofysiologiska aktivitet registreras med patch-clamp. Det slutna mikroflödessystemet med integrerad mikropipett, kopplades till ett pumpsystem för införandet av celler och buffert med olika kemiska egenskaper och syrehalter. I ett inverterat mikroskop integrerades optisk pincett, UV-Vis spektrometer och patch-clamp. Resultat och diskussion: För att pröva konceptet fångades och fördes en röd blodcell optiskt mot mikropipetten som befann sig på en fast position i mikroflödescellen. Cellens syrebindningstillstånd varierades genom att tillsätta syrefri eller syresatt buffert och registrerades med UV-Vis spektrometern. I ett vidare experiment manipulerades en nervcell optiskt i ett öppet system mot patch-clamp pipetten och elektrofysiologiska mätningar utfördes. Vi kunde verifiera att den optiska pincetten inte påverkade den elektrofysiologiska mätningen. För närvarandet utförs elektrofysiologiska mätningar i det slutna mikroflödessystemet för att se hur nervcellerna reagerar under varierande syrehalt. Genom mätningarna hoppas vi att få mer kunskap om försvarsmekanismerna som igångsätts av neuroner under syrefattiga förhållanden.

  • 7. Alrifaiy, Ahmed
    et al.
    Lindahl, Olof
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ett mikroflödessystem med optisk pincett och UV- vis för studier på enskilda biologiska celler2010Conference paper (Other academic)
  • 8.
    Alrifaiy, Ahmed
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Patch-clamp electrophysiological measurements on single cells under hypoxic conditions in microfluidic systems2012Conference paper (Refereed)
  • 9.
    Alrifaiy, Ahmed
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Polymer-based microfluidic devices for pharmacy, biology and tissue engineering2012In: Polymers, ISSN 2073-4360, E-ISSN 2073-4360, Vol. 4, no 3, p. 1349-1398Article in journal (Refereed)
    Abstract [en]

    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.

  • 10.
    Alrifaiy, Ahmed
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    How to integrate a micropipette into a closed microfluidic system: absorption spectra of an optically trapped erythrocyte2011In: Biomedical Optics Express, ISSN 2156-7085, E-ISSN 2156-7085, Vol. 2, no 8, p. 2299-2306Article in journal (Refereed)
    Abstract [en]

    In July 2011 a new concept of a closed microfluidic system equipped with a fixed micropipette, optical tweezers and a UV-Vis spectrometer was presented [Biomed. Opt. Express 2, 2299 (2011)]. Figure 1 showed falsely oriented mirrors. To clarify the design of the setup, this erratum presents a correct schematic

  • 11.
    Baumgarten, Matthias
    et al.
    University of Ulster.
    Guldenring, Daniel
    University of Ulster.
    Nugent, Chris
    University of Ulster.
    Hallberg, Josef
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Embedding self-awareness into objects of daily life: the smart kettle2010In: 6th International Conference on Intelligent Environments: IE 2010 : Kuala Lumpur; 19 July 2010 - 21 July 2010, Los Alamitos, Calif, 2010, p. 34-39Conference paper (Refereed)
    Abstract [en]

    Intelligent Environments on varying scales and for different purposes are slowly becoming a reality. In the near future, global smart world infrastructures will become a commodity that will support various activities of daily life at different degrees of realism. Such infrastructures have the potential to offer dedicated, context- and situation-aware information and services by simultaneously providing the next-generation of data collection, execution and service provisioning layers. One key aspect of this vision is the correct monitoring and understanding of how people interact with their environment; how they can actually benefit from the added intelligence; and finally how future services can be improved or better personalized to enhance human environment interaction as a whole. This level of intelligence is of particular relevance in the health and social care domain where person-centric services can be deployed to assist or even enable a person in performing activities of daily living. This paper discusses the concept of embedded self-aware profiles for smart devices that can be used to gain a deeper contextual understanding of their use and also discusses the emergence of a general model of Ambient Intelligence that is based on the collective existence and behavior of such smart devices. Although generic in principle, the proposed concepts have been exemplified by a distinct use case, namely a smart kettle.

  • 12.
    Bitaraf, Nazanin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    The electrophysiological response of medial preoptic neurons to hypoxia and development of a system for patch-clamp measurement with full oxygen control2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    A stroke is caused by interruption of the blood supply to the brain. Yearly 15 million people around the globe endure a stroke and the costs and suffering for the people involved and the society are immense. The aim of this thesis was to investigate the response to oxygen deprivation in neurons from the medial preoptic nucleus (MPN) that have a high abundance of neuroglobin. The long term goal is to investigate the neuroprotective role of the protein in relation to stroke. Initially, the electrophysiological response of neurons to hypoxic exposure in an open system was assessed with a conventional patch-clamp setup. The first aim was to see how well the conventional system worked and if it needed improvement. Secondly, the MPN had never been investigated regarding oxygen, deprivation; hence the electrophysiological response under hypoxia needed to be investigated. The conventional patch-clamp system only allowed a reduction of the oxygen content to a level of 3-6% but not total control of the cell environment. The medial preoptic neurons showed mainly an increase of their resting membrane potential at hypoxia. The voltage activated Ca2+ and K+ currents displayed a clear attenuation when cells were subjected to hypoxia. Non-L-type Ca2+ channels were affected by hypoxic exposure and one cell indicated participation of Ca2+ activated K+ channels. However, a response could only be seen in approximately fifty percent of the neurons in the open system. This may have been due to the fact that full control of the oxygen around the neurons at hypoxia could not be achieved. A new system with full control of the ambient oxygen had to be developed in order to investigate this. After the conclusions of the first experiments, a system was developed were a labon- a-chip system was combined with the patch-clamp technique. A microfluidic system with a patch-clamp micropipette integrated was combined with optical tweezers for 3D maneuvering of the neurons. The development of patch-clamp in combination with a microfluidic system and optical tweezers allowed for full oxygen control. The experiments showed that the electrophysiological measurements were not affected by the laser when an infrared laser was used. The microfluidic system allowed very good oxygen control reaching levels of 0.5-1.5 % compared to 3-6 % in the open system. In summary, this work suggests that high voltage activated Ca2+ channels, and K+ channels are involved in the hypoxic depolarization of medial preoptic neurons. Full control of ambient oxygen in cell vicinity could be achieved by the combination of microfluidics, patch-clamp and optical tweezers. The results can be used in future studies to better understand the reaction of the brain to oxygen deprivation caused by stroke.

  • 13.
    Bitaraf, Nazanin
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Alrifaiy, Ahmed
    Luleå tekniska universitet.
    Druzin, Mikhail
    Umeå University, Department of Integrative Medical Biology, Physiology.
    Ramser, Kerstin
    Development of a multifunctional microfluidic system for studies of nerve cell activity during hypoxic and anoxic conditions2009In: World Congress on Medical Physics and Biomedical Engineering: September 7 - 12, 2009, Munich, Germany, Berlin: Springer Science+Business Media B.V., 2009, Vol. 8, p. 176-179Conference paper (Refereed)
  • 14. Bitaraf, Nazanin
    et al.
    Druzin, Mikhail
    Umeå University, Integrative Medical Biology, Physiology.
    Lindahl, Olof
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Elektrofysiologiska mätningar på MPN-neuroner under hypoxi: ett steg mot profylaktisk behandling av patienter i riskzonen för stroke2010In: Medicinteknikdagarana 2010, 2010Conference paper (Other academic)
  • 15. Bitaraf, Nazanin
    et al.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Alrifaiy, Ahmed
    Multipla mätningar på enstaka celler i ett mikroflödessystem2009Conference paper (Other academic)
  • 16.
    Candefjord, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Combining a resonance and a Raman sensor: towards a new method for localizing prostate tumors in vivo2007Report (Other academic)
    Abstract [en]

    Prostate cancer is the most common malignancy diagnosed in western men today. Measuring the amount of prostate-specific antigen in blood is the most widespread tool for diagnosing prostate cancer early on. However, clinical investigations show that many people with high levels of PSA can be healthy and vice versa. Ultrasound-guided biopsies is the clinical method used to prove prostate cancer. Unfortunately, many tumors are overlooked by this procedure. It has been estimated that about 30% of the biopsy examinations fail to find a present tumor. The resonance technique, which can differentiate hard and soft materials, has in vitro been shown to be able to distinguish prostate cancer and healthy epithelial prostate tissue. Raman spectroscopy is also a good candidate for detecting prostate cancer. Our novel idea of combining the resonance and Raman techniques into a portable probe, appropriate for in vivo examinations of the prostate, will be discussed in this report. The two techniques are presented and explained, and the feasibility of combining them is discussed. Planned experiments and investigations are outlined.

  • 17.
    Candefjord, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Combining the tactile resonance method and Raman spectroscopy for tissue characterization towards prostate cancer detection2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Prostate cancer (PCa) is the most common male cancer in Europe and the US, and only lung and colorectal cancer have a higher mortality among European men. In Sweden, PCa is the most common cause of cancer-related death for men.The overall aim of this thesis was to explore the need for new and complementary methods for PCa detection and to take the rst step towards a novel approach: combining the tactile resonance method (TRM) and Raman spectroscopy (RS). First, the main methods for PCa detection were reviewed. Second, to establish a robust protocol for RS experiments in vitro, the eects of snap-freezing and laser illumination on porcine prostate tissue were studied using RS and multivariate statistics. Third, measurements on porcine and human tissue were performed to compare the TRM and RS data via multivariate techniques, and to assess the accuracy of classifying healthy and cancerous tissue using a support vector machine algorithm.It was concluded through the literature review that the gold standard for PCa detection and diagnosis, the prostate specic antigen test and systematic biopsy, have low sensitivity and specicity. Indolent and aggressive tumors cannot be reliably dierentiated, and many men are therefore treated either unnecessarily or too late. Clinical benets of the state-of-the-art in PCa imaging - advanced ultrasound and MR techniques - have still not been convincingly shown. There is a need for complementary and cost-eective detection methods. TRM and RS are promising techniques, but hitherto their potential for PCa detection have only been investigated in vitro.In the RS study no evidence of tissue degradation due to 830 nm laser illumination at an irradiance of ∼3 · 1010 W m-2 were found. Snap-freezing and subsequent storage at -80° C gave rise to subtle but signicant changes in Raman spectra, most likely related to alterations in the protein structure. The major changes due to PCa do not seem to be related to the protein structure, hence snap-freezing may be applied in our experiments.The combined measurements on porcine and human prostate tissue showed that RS provided additional discriminatory power to TRM. The classication accuracy for healthy porcine prostate tissue, and for healthy and cancerous human prostate tissue, was > 73%. This shows the power of the support vector machine applied to the combined data.In summary, this work indicates that an instrument combining TRM and RS is a promising complementary method for PCa detection. Snap-freezing of samples may be used in future RS studies of PCa. A combined instrument could be used for tumor-border demarcation during surgery, and potentially for guiding prostate biopsies towards lesions suspicious for cancer. All of this should provide a more secure diagnosis and consequently more effcient treatment of the patient.

  • 18.
    Candefjord, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Towards new sensors for prostate cancer detection: combining Raman spectroscopy and resonance sensor technology2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Prostate cancer (PCa) is the most common male cancer in Europe and the US, and only lung and colorectal cancer have a higher mortality among European men. In Sweden, PCa is the most common cause of cancer-related death for men.The overall aim of this licentiate work was to explore the need for new and complementary methods for PCa detection and to take the first step towards a novel approach: combining Raman spectroscopy and resonance sensor technology. Firstly, the main methods for PCa detection were reviewed. Secondly, to establish a robust protocol for Raman experiments in vitro, the effects of snap-freezing and laser illumination on porcine prostate tissue were studied using Raman spectroscopy and multivariate statistics. Thirdly, measurements on pork belly tissue using both a resonance sensor and a Raman fiberoptic probe were evaluated regarding correlation of the data.It was concluded that the gold standard for PCa detection and diagnosis, the prostate specific antigen test and systematic biopsy, have low sensitivity and specificity. Indolent and aggressive tumors cannot be reliably differentiated, and many men are therefore treated either unnecessarily or too late. Clinical benefits of the state-of-the-art in PCa imaging - advanced ultrasound and MR techniques - have still not been convincingly shown. There is a need for complementary and cost-effective detection methods. Raman spectroscopy and resonance sensor technology are promising alternative techniques, but hitherto their potential for PCa detection have only been investigated in vitro.No evidence of tissue degradation due to 830 nm laser illumination at an irradiance of 3 1010 W/m2 were found. Snap-freezing and subsequent storage at -80◦C gave rise to subtle but significant changes in Raman spectra, most likely related to alterations in the protein structure. The major changes in cancerous prostate tissue do not seem to be related to the protein structure, hence snap-freezing may be applied.The combined measurements on pork belly tissue showed that Raman spectroscopy provided additional discriminatory power to the resonance sensor. The Raman data explained 67% of the variability of the stiffness parameter. The differentiation of tissue types using the resonance sensor was relatively poor, likely due to its large sample volume compared to the Raman sensor. A smaller resonance sensor tip may improve the results.In summary, this work indicates that an instrument combining Raman spectroscopy and resonance sensor technology is a promising complementary method for PCa detection. Snap-freezing of samples may be used in future Raman studies of PCa. A combined instrument could potentially be used to guide prostate biopsies towards lesions suspicious for cancer, and for tumor-border demarcation during surgery. All of this should provide a more secure diagnosis and consequently more efficient treatment of the patient.

  • 19.
    Candefjord, Stefan
    et al.
    Chalmers University of Technology.
    Murayama, Yoshinobu
    College of Engineering, Nihon University.
    Nyberg, Morgan
    Hallberg, Josef
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Ljungberg, Börje
    Umeå University, Department of Surgical and Perioperative Science, Urology and Andrology.
    Bergh, Anders
    Department of Medical Biosciences Pathology, Umeå University.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Combining scanning haptic microscopy and fibre optic Raman spectroscopy for tissue characterisation2012In: Journal of Medical Engineering & Technology, ISSN 0309-1902, E-ISSN 1464-522X, Vol. 36, no 6, p. 319-327Article in journal (Refereed)
    Abstract [en]

    The tactile resonance method (TRM) and Raman spectroscopy (RS) are promising for tissue characterisation in vivo. Our goal is to combine these techniques into one instrument, to use TRM for swift scanning, and RS for increasing the diagnostic power. The aim of this study was to determine the classification accuracy, using support vector machines, for measurements on porcine tissue and also produce preliminary data on human prostate tissue. This was done by developing a new experimental setup combining micro-scale TRM — scanning haptic microscopy (SHM) — for assessing stiffness on a micro-scale, with fibre optic RS measurements for assessing biochemical content. We compared the accuracy for using SHM alone versus SHM combined with RS, for different degrees of tissue homogeneity. The cross-validation classification accuracy for healthy porcine tissue types using SHM alone was 65–81%, and when RS was added it was increased to 81–87%. The accuracy for healthy and cancerous human tissue was 67–70% when only SHM was used, and increased to 72–77% for the combined measurements. This shows that the potential for swift and accurate classification of healthy and cancerous prostate tissue is high. This is promising for developing a tool for probing the surgical margins during prostate cancer surgery.

  • 20.
    Candefjord, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Nyberg, Morgan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Jalkanen, Ville
    Umeå University. Department of Applied Physics and Electronics.
    Ramser, Kerstin
    Lindahl, Olof
    Combining fibre optic Raman spectroscopy and tactile resonance measurement for tissue characterization2010In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 21, no 12Article in journal (Refereed)
    Abstract [en]

    Tissue characterization is fundamental for identification of pathological conditions. Raman spectroscopy (RS) and tactile resonance measurement (TRM) are two promising techniques that measure biochemical content and stiffness, respectively. They have potential to complement the golden standard-–histological analysis. By combining RS and TRM, complementary information about tissue content can be obtained and specific drawbacks can be avoided. The aim of this study was to develop a multivariate approach to compare RS and TRM information. The approach was evaluated on measurements at the same points on porcine abdominal tissue. The measurement points were divided into five groups by multivariate analysis of the RS data. A regression analysis was performed and receiver operating characteristic (ROC) curves were used to compare the RS and TRM data. TRM identified one group efficiently (area under ROC curve 0.99). The RS data showed that the proportion of saturated fat was high in this group. The regression analysis showed that stiffness was mainly determined by the amount of fat and its composition. We concluded that RS provided additional, important information for tissue identification that was not provided by TRM alone. The results are promising for development of a method combining RS and TRM for intraoperative tissue characterization.

  • 21. Candefjord, Stefan
    et al.
    Nyberg, Morgan
    Jalkanen, Ville
    Umeå University. Department of Applied Physics and Electronics.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Evaluating the use of a Raman fiberoptic probe in conjunction with a resonance sensor for measuring porcine tissue in vitro2009In: World Congress on Medical Physics and Biomedical Engineering: September 7 - 12, 2009, Munich, Germany / [ed] Olaf Dössel; Wolfgang C. Schlegel, Berlin: Springer Science+Business Media B.V., 2009, Vol. 7, p. 414-417Conference paper (Refereed)
    Abstract [en]

    Prostate cancer is the most common form of cancer and the third leading cause of cancer-related death in European men. There is a need for new methods that can accurately localize and diagnose prostate cancer. In this study a new approach is presented: a combination of resonance sensor technology and Raman spectroscopy. Both methods have shown promising results for prostate cancer detection in vitro. The aim of this study was to evaluate the combined information from measurements with a Raman fiberoptic probe and a resonance sensor system. Pork belly tissue was used as a model system. A three-dimensional translation table was equipped with an in-house developed software, allowing measurements to be performed at the same point using two separate instruments. The Raman data was analyzed using principal component analysis and hierarchical clustering analysis. The spectra were divided into 5 distinct groups. The mean stiffness of each group was calculated from the resonance sensor measurements. One of the groups differed significantly (p < 0.05) from the others. A regression analysis, with the stiffness parameter as response variable and the principal component scores of the Raman data as the predictor variables, explained 67% of the total variability. The use of a smaller resonance sensor tip would probably increase the degree of correlation. In conclusion, Raman spectroscopy provides additional discriminatory power to the resonance sensor

  • 22. Candefjord, Stefan
    et al.
    Nyberg, Morgan
    Jalkanen, Ville
    Umeå universitet.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Kombinationsinstrument för detektering av prostatacancer: korrelation mellan resonanssensor och fiberoptisk Ramanprobe2009Conference paper (Other academic)
  • 23.
    Candefjord, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Lindahl, Olof
    Effects of snap-freezing and laser illumination of tissue on near-infrared Raman spectra of porcine prostate tissue2008Conference paper (Other academic)
  • 24. Candefjord, Stefan
    et al.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Effects of snap-freezing and near-infrared laser illumination on porcine prostate tissue as measured by Raman spectroscopy2009In: The Analyst, ISSN 0003-2654, E-ISSN 1364-5528, Vol. 134, no 9, p. 1815-1821Article in journal (Refereed)
    Abstract [en]

    Most Raman spectroscopic studies on tissue are performed in vitro. To assure that the results are applicable to in vivo examinations, preparation protocols and measurement procedures of tissue for in vitro studies should preserve tissue characteristics close to the native state. This study had two aims. The first was to elucidate if photoinduced effects arise during 5 minutes' continuous illumination of tissue with an 830 nm laser at an irradiance of 3 × 1010 W/m2. The second was to investigate the effects of snap-freezing of porcine prostate tissue in liquid nitrogen and subsequent storage at -80 °C, by means of multivariate analysis. 830 nm laser illumination of the specified irradiance did not affect the Raman spectra. A decrease of the spectral background was observed, likely due to photobleaching of tissue fluorophores. Snap-freezing and subsequent storage at -80 °C gave rise to subtle but significant alterations in Raman spectra, most likely related to changes in the protein conformations

  • 25.
    Candefjord, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Lindahl, Olof
    En ny metod för att lokalisera och diagnostisera prostatacancer2007In: Medicinteknikdagarna, 2007, p. 33-34Conference paper (Other academic)
  • 26.
    Candefjord, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Kombinationsinstrument för detektering av prostatacancer: mätningar på snitt av grisprostata med resonanssensor och fiberoptisk Ramanprobe2010Conference paper (Refereed)
  • 27. Candefjord, Stefan
    et al.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Technologies for localization and diagnosis of prostate cancer2009In: Journal of Medical Engineering & Technology, ISSN 0309-1902, E-ISSN 1464-522X, Vol. 33, no 8, p. 585-603Article in journal (Refereed)
    Abstract [en]

    The gold standard for detecting prostate cancer (PCa), systematic biopsy, lacks sensitivity as well as grading accuracy. PSA screening leads to over-treatment of many men, and it is unclear whether screening reduces PCa mortality. This review provides an understanding of the difficulties of localizing and diagnosing PCa. It summarizes recent developments of ultrasound (including elastography) and MRI, and discusses some alternative experimental techniques, such as resonance sensor technology and vibrational spectroscopy. A comparison between the different methods is presented. It is concluded that new ultrasound techniques are promising for targeted biopsy procedures, in order to detect more clinically significant cancers while reducing the number of cores. MRI advances are very promising, but MRI remains expensive and MR-guided biopsy is complex. Resonance sensor technology and vibrational spectroscopy have shown promising results in vitro. There is a need for large prospective multicentre trials that unambiguously prove the clinical benefits of these new techniques.

  • 28.
    Candefjord, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Lindahl, Olof
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Towards new sensors for cancer detection in vivo, a handheld detector combining a bre-optic Raman probe and a resonance sensor2007Conference paper (Refereed)
  • 29.
    Damber, Jan-Erik
    et al.
    Umeå University, Department of Physiology.
    Bergh, Anders
    Umeå University, Department of Physiology.
    Fagrell, Bengt
    Danderyds sjukhus.
    Lindahl, Olof
    Rooth, Pål
    Umeå University, Department of Histology and Cell Biology.
    Testicular microcirculation in the rat studied by videophotometric capillaroscopy, fluorescence microscopy and laser Doppler flowmetry1986In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 126, no 3, p. 371-6Article in journal (Refereed)
    Abstract [en]

    Testicular capillary blood flow was studied in rats using laser Doppler flowmetry, in vivo fluorescence microscopy and videophotometric capillaroscopy. All the methods revealed rhythmical oscillations in testicular microcirculation with a periodicity of 4-10 c.p.m. In arterioles, capillaries and small post-capillary vessels, periods of continuous blood flow alternated with periods of no or very low flow. No visible leakage of dextran-150 was observed from the testicular blood vessels. Four, 8 and 16 h after an s.c. injection of 200 IU hCG the blood flow was continuous and there was leakage of dextran-150 from the microvessels to the interstitial tissue. Twenty-four and 32 h after hCG the blood flow pattern was again rhythmical, and at 32 h there was no leakage of dextran-150. This suggests that hCG induces changes in blood flow and transvascular fluid exchange in the testis, perhaps by altering smooth muscle activity at the arteriolar-level.

  • 30.
    Damber, Jan-Erik
    et al.
    Umeå University, Department of Physiology.
    Lindahl, Olof
    Selstam, Gunnar
    Umeå University, Department of Physiology.
    Tenland, Torsten
    Umeå University, Department of Physiology.
    Rhythmical oscillations in rat testicular microcirculation as recorded by laser Doppler flowmetry1983In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 118, no 2, p. 117-23Article in journal (Refereed)
    Abstract [en]

    We have earlier reported that local testicular blood flow, recorded by laser Doppler flowmetry, shows large oscillations with a frequency of 5-10 min-1. In the present study it is proposed that the recorded oscillations represent mainly local microvascular blood flow variations rather than variations in total testicular blood flow or tissue movements. The reasons for this are: (a) Blood flow simultaneously measured at two separate sites showed oscillations with different frequencies. (b) A local subcapsular injection of room-tempered saline under one probe site eradicated oscillations under that probe but not under another adjacent probe. (c) When the testicular capsule was split open, recordings of blood flow continued to show oscillations. (d) The amplitude of the oscillations was rather large (peak to peak value about 50% of mean flow value). No movements of the testicular surface were seen. A 20 min continuous infusion of 0.4 microgram/min noradrenaline did induce a decrease in plasma testosterone concentration, but did not change the mean blood flow. However, the oscillations nearly completely disappeared during the infusion period. The present study also shows that laser Doppler flowmetry is a versatile method and the rat testis provides a suitable organ in the study of the origin and functional importance of these oscillations

  • 31.
    Damber, Jan-Erik
    et al.
    Umeå University, Department of Physiology.
    Lindahl, Olof
    Selstam, Gunnar
    Umeå University, Department of Physiology.
    Tenland, Torsten
    Umeå University, Department of Physiology.
    Testicular blood flow measured with a laser Doppler flowmeter: acute effects of catecholamines.1982In: Acta Physiologica Scandinavica, ISSN 0001-6772, E-ISSN 1365-201X, Vol. 115, no 2, p. 209-15Article in journal (Refereed)
    Abstract [en]

    Laser Doppler flowmetry was used to continuously measure testicular blood flow in rats. The method was found applicable on surgically exposed testes. Regular oscillations in blood flow, with a periodicity of 8.6 +/- 0.7 cycles per minute (mean +/- SD), were observed in recordings from 22 to 23 rats. Clamping of the testicular artery reduced the blood flow signal to background values. Effects of catecholamines administered into the tail artery on testicular blood flow together with systemic effects on mean arterial blood pressure and heart rate were measured. It was found that noradrenaline as well as adrenaline caused a significant decrease in blood flow when 10 micrograms was injected. Only noradrenaline decreased the blood flow when 1 microgram was given. The large oscillations detected in the blood flow recordings disappeared quickly when 10 or 1 micrograms of both hormones was administered. It was concluded that catecholamines can exert rapid effects on testicular blood flow

  • 32. Drugge, Mikael
    et al.
    Hallberg, Josef
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Parnes, Peter
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Synnes, Kåre
    Wearable systems in nursing home care: prototyping experience2006In: IEEE pervasive computing, ISSN 1536-1268, E-ISSN 1558-2590, Vol. 5, no 1, p. 86-91Article in journal (Refereed)
    Abstract [en]

    The development of a wearable prototype systems after studies conducted in a nursing home care is discussed. The specific problems encountered by medical workers at nursing homes includes communication, information dissemination, access to patient charts and organizational issues. The failure of which may cause stress, discomfort, and dissatisfaction among caretakers and patients as well as possible detrimental health consequences for patients. A Wizard of Oz experiments was used to retrieve information, process interrupting phone calls, to simplify communication with others, and to minimize the interaction needed with the wearable computer.

  • 33. Drugge, Mikael
    et al.
    Hallberg, Josef
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Synnes, Kåre
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Parnes, Peter
    Relieving the medical workers' daily work through wearable and pervasive computing2005In: ICE2005: the 11th International Conference on Concurrent Enterprising : integrated engineering of products, services and organisations, Munich, Germany 20-22 June 2005, Nottingham: Centre for concurrent enterprising, University of Nottongham , 2005Conference paper (Refereed)
    Abstract [en]

    We intend to relieve the daily work at care-centers, allowing medical workers to focus on the patients and their needs. This goal can be achieved by employing technology that automate and simplify tasks previously requiring tedious interventions, giving more time for the important human to human interaction. For any technology to become accepted by the medical workers, we must ensure that it is highly natural and unobtrusive, without interfering with their caregiving. By studying the medical workers’ daily work, we can draw conclusions on what problems they encounter, allowing us to develop prototypes which can be deployed and used at the care-centers. In doing this, we can proceed to study the acceptance and usability of our proposed solution, and see whether and how it solves the problem. In this position paper, we present our current and future research in wearable and pervasive health-care.

  • 34.
    Eklund, Abders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering.
    Bäcklund, Tomas
    Umeå University Hospital, Department of Biomedical Engineering.
    Lindahl, Olof
    Resonanssensor för bestämning av intraokulärt tryck1999In: Program & sammanfattningar. [56]: Stockholmsmässan, Älvsjö 30 nov - 2 dec 1999, Stockholm: Svenska läkaresällskapet , 1999, p. 243-Conference paper (Other academic)
  • 35.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering.
    Bergh, Anders
    Umeå University Hospital, Department of Pathology.
    Lindahl, Olof
    A catheter tactile sensor for measuring hardness of soft tissue: measurement in a silicone model and in an in vitro human prostate model1999In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 37, no 5, p. 618-24Article in journal (Refereed)
    Abstract [en]

    Tissue hardness is related to tissue composition, and this is often changed by disease. It is therefore of interest to measure the hardness in an objective and non-invasive way. A tactile sensor based on a vibrating piezoelectric ceramic element in a feedback loop is described. When the sensor touches an object it produces a frequency shift related to the hardness of the object. The aim of this study was to develop an in vitro hardness measurement method using a catheter type version of the sensor. The method was evaluated in an established silicone tissue model and on human prostate tissue in vitro. A linear relationship was found with a high degree of explanation (R2 = 0.98) between a cone penetration hardness standard (DIN ISO 2137) applied to the silicone model and the corresponding frequency shift. The results from measurements on a human prostate tissue sample, fixed with formalin, showed that the relative hardness measured with the tactile sensor correlated (R = -0.96, p < 0.001, N = 60) with the proposed hardness related to the histological composition of the prostate tissue. The results indicated that hardness of prostate tissue, and maybe hardness of human tissue in general, can be expressed according to the cone penetration standard and that the hardness can be measured with this tactile sensory system. These findings hold the promise of further development of a non-invasive tool for hardness measurement in a clinical situation

  • 36.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering.
    Bergh, Anders
    Umeå University Hospital, Department of Biomedical Engineering.
    Lindahl, Olof
    A resonator sensor for evaluation of prostate tissue composition and hardness1999In: Proceedings of the 11th Nordic-Baltic conference on biomedical engineering.: 6-10 June 1999, Tallin, Estonia, 1999, p. 181-182Conference paper (Other academic)
  • 37.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering.
    Bergh, Anders
    Umeå University Hospital, Department of Biomedical Engineering.
    Lindahl, Olof
    Vibrationssensor för värdering av vävnadsmjukhet1998In: Program & sammanfattningar. [55]: 24-26 november 1998 i Göteborg, Stockholm: Svenska läkaresällskapet , 1998, p. 259-Conference paper (Other academic)
  • 38.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Bäcklund, Tomas
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Lindahl, Olof
    A resonator sensor for measurement of intraocular pressure: evaluation in an in vitro pig-eye model.2000In: Physiological Measurement, ISSN 0967-3334, E-ISSN 1361-6579, Vol. 21, no 3, p. 355-367Article in journal (Refereed)
    Abstract [en]

    Intraocular pressure (IOP) measurement is performed routinely at every eye clinic. High IOP, which can be a sign of glaucoma, can lead to degeneration of the retina and can cause blindness. In this study we developed a resonator sensor for IOP measurement based on an oscillator consisting of a piezoelectric element made of lead zirconate titanate, a flat contact piece of nylon and a feedback circuit. The aim of this study was to evaluate the new sensor's ability to determine lOP in an in vitro pig-eye model. Six eyes from four pigs were removed and fixed in agar. They were then pressurized by a saline column (10-35 cm H2O) through a cannula inserted into the vitreous chamber. The IOP was measured with the resonator sensor applied to cornea. An Alcon applanation pneumatonometer and a standard Viggo-Spectramed pressure sensor connected to the saline column were used as references. The IOP as measured with the resonator sensor correlated well with the pressure elicited by the saline column for individual eyes (r = 0.96-0.99, n = 60) and for all eyes (r = 0.92, n = 360). The correlation between the resonance sensor and the pneumatonometer was r = 0.92 (n = 360). The pneumatonometer also showed a good correlation with the saline column (r = 0.98, n = 360). We conclude that our in vitro pig-eye model made it possible to induce reproducible variation in IOP, and measurement of that pressure with the newly developed resonator sensor gave very promising results for development of a clinically applicable IOP tonometer with unique properties.

  • 39.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering.
    Bäcklund, Tomas
    Umeå University Hospital, Department of Biomedical Engineering.
    Lindahl, Olof
    Resonator sensor for measurement of intraocular pressure2000In: World Congress on Medical Physics and Biomedical Engineering,: July 23-28, 2000, Chicago, USA, 2000Conference paper (Other academic)
  • 40.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering.
    Bäcklund, Tomas
    Umeå University Hospital, Department of Biomedical Engineering.
    Lindahl, Olof
    Lindén, Christina
    Umeå University, Centre for Biomedical Engineering and Physics.
    Resonanssensor för bestämning av intraokulärt tryck2000In: Program & sammanfattningar. [57]: Svenska mässan, Göteborg, 29 november-1 december 2000, Stockholm: Svenska läkaresällskapet , 2000, p. 249-Conference paper (Other academic)
  • 41.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Hallberg, Per
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Lindén, Christina
    Umeå University, Department of Clinical Science, Ophthalmology.
    Bäcklund, Tomas
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Lindahl, Olof
    Evaluation of an applanation resonator sensor for intraocular pressure measurement in a clinical setting2004In: World Congress on Medical Physics and Biomedical Engineering, 2004Conference paper (Other academic)
  • 42.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Hallberg, Per
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Lindén, Christina
    Umeå University, Center for Biomedical Engineering and Physics.
    Lindahl, Olof
    An applanation resonator sensor for measuring intraocular pressure using combined continuous force and area measurement2003In: Investigative Ophthalmology and Visual Science, ISSN 0146-0404, E-ISSN 1552-5783, Vol. 44, no 7, p. 3017-24Article in journal (Refereed)
    Abstract [en]

    PURPOSE: For diagnostic purposes and for follow-up after treatment, it is important to have simple and reliable methods for measuring intraocular pressure (IOP). The purpose of this study was to develop a new applanation method for IOP measurement that uses combined continuous force and area measurement and to develop and evaluate an applanation resonator sensor (ARS) tonometer based on that method. METHODS: The tonometer was developed and evaluated in an in vitro porcine eye model, in which enucleated eyes were pressurized with a saline column. A model assuming that the applanation principle is valid over a certain interval of contact area was proposed. Continuous contact area was measured with a resonator sensor device, and contact force was measured with a force transducer, both mounted together in one probe. Reference IOP was measured in the vitreous chamber (IOP(VC)) with a standard fluid pressure transducer. RESULTS: An optimization algorithm determined the applanation interval that was optimal for calculating IOP(ARS). The corresponding time interval was 30 +/- 3 to 77 +/- 4 ms (mean +/- SD, n = 418) after initial contact. The proposed model showed a degree of explanation of R(2 [supi]) = 0.991 (n = 410, six eyes), corresponding to a correlation of r = 0.995 (n = 410) between IOP(ARS) and IOP(VC). The within-eyes precision (i.e., 95% confidence interval for the residuals between IOP(ARS) and IOP(VC)) was +/- 1.8 mm Hg (n = 410, six eyes). CONCLUSIONS: In this study, the ARS method for measuring IOP was evaluated in an in vitro porcine eye model and showed high precision. The ARS method is, to the authors' knowledge, the first to combine simultaneous, continuous sampling of both parameters included in the applanation principle: force and area. Consequently, there is a potential for reducing errors in clinical IOP tonometry.

  • 43.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Lindahl, Olof
    Umeå universitet.
    Method and device for determining the intraocular pressure, by measuring the changing of the frequency characteristicsPatent (Other (popular science, discussion, etc.))
    Abstract [en]

    The present invention relates to a method and a device for measuring the pressure p in an eye, the so-called intraocular pressure. The method includes a contact body with a known geometry being pressed against the eye with a gradually increasing contact force F and that when the area of deformation of the eye A can be determined, the pressure can be obtained from the relation P=F/A, whereby the frequency characteristic of a contact body associated with a sensor system oscillating in resonance is read, the contact body is pressed against the eye to form a new system oscillating in resonance, the contact force and frequency characteristic for the new system is read, and the change in frequency characteristic is calculated. In this way, the pressure of the eye can be determined since the sought deformation area A is a function of the change A(.function..sub.i ch ar!). The device has a contact body (4) for pressing against the eye (1) and a means (3) of determining the force with which the contact body is pressed against the eye, whereby the contact body (4) is part of a system oscillating in resonance, and the resonance system is connected to a means (9) for reading the frequency characteristic of the system.

  • 44.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Lindahl, Olof
    Umeå universitet.
    Metod och anordning för bestämning av det intraokulära trycket, med hjälp av förändringen av frekvenskarakteristikenPatent (Other (popular science, discussion, etc.))
  • 45.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Lindahl, Olof
    Umeå universitet.
    Metod och anordning för brestämning av det intraokulära trycket, med hjälp av förändringen av frekvenskaraktäristikenPatent (Other (popular science, discussion, etc.))
  • 46.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering.
    Lindahl, Olof
    Bäcklund, Tomas
    Umeå University Hospital, Department of Biomedical Engineering.
    Omata, Sadao
    Nihon University.
    Development of catheter tactile sensor for detecting stiffness of inner organ using piezoelectric element1997In: World Congress on Medical Physics and Biomedical Engineering: Nice, France, 14.-19.09.1997, 1997, p. 1281-Conference paper (Other academic)
  • 47.
    Eklund, Anders
    et al.
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Lindén, Christina
    Umeå University, Department of Clinical Science, Ophthalmology.
    Bäcklund, Tomas
    Umeå University Hospital, Department of Biomedical Engineering & Informatics.
    Andersson, Britt M.
    Umeå University. Department of Applied Physics and Electronics.
    Lindahl, Olof
    Evaluation of applanation resonator sensors for intra-ocular pressure measurement: results from clinical and in vitro studies2003In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 41, no 2, p. 190-7Article in journal (Refereed)
    Abstract [en]

    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.

  • 48. Enger, Jonas
    et al.
    Goksör, Mattias
    Ramser, Kerstin
    Hagberg, Petter
    Hanstorp, Dag
    Optical tweezers applied to a microfluidic system2004In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 4, no 3, p. 196-200Article in journal (Refereed)
    Abstract [en]

    We will demonstrate how optical tweezers can be combined with a microfluidic system to create a versatile microlaboratory. Cells are moved between reservoirs filled with different media by means of optical tweezers. We show that the cells, on a timescale of a few seconds, can be moved from one reservoir to another without the media being dragged along with them. The system is demonstrated with an experiment where we expose E. coli bacteria to different fluorescent markers. We will also discuss how the system can be used as an advanced cell sorter. It can favorably be used to sort out a small fraction of cells from a large population, in particular when advanced microscopic techniques are required to distinguish various cells. Patterns of channels and reservoirs were generated in a computer and transferred to a mask using either a sophisticated electron beam technique or a standard laser printer. Lithographic methods were applied to create microchannels in rubber silicon (PDMS). Media were transported in the channels using electroosmotic flow. The optical system consisted of a combined confocal and epi-fluorescence microscope, dual optical tweezers and a laser scalpel.

  • 49.
    Enman, Josefine
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Patra, Anuttam
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Rova, Ulrika
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Solid state characterization of sodium eritadenate2011In: American Journal of Analytical Chemistry, ISSN 2156-8251, E-ISSN 2156-8278, Vol. 2, no 2, p. 164-173Article in journal (Refereed)
    Abstract [en]

    Knowledge of the solid state is of great importance in the development of a new active pharmaceutical ingredient, since the solid form often dictates the properties and performance of the drug. In the present study, solid state characteristics of the sodium salt of the candidate cholesterol reducing compound eritadenine, 2(R), 3(R))-dihydroxy-4-(9-adenyl)-butanoic acid, were investigated. The compound was crystallized by slow cooling from water and various aqueous ethanol solutions, at different temperatures. Further, the compound solution was subjected to lyophilization and to high vacuum drying. The resulting solids were screened for polymorphism by micro Raman spectroscopy (λex = 830 nm) and the crystallinity was investigated by X-ray powder diffraction. Further, thermal analysis was applied to study possible occurrence of solvates or hydrates. Solids obtained from slow cooling showed crystallinity, whereas rapid cooling gave rise to more amorphous solids. Analysis of difference spectra of the Raman data for solids obtained from slow cooling of solution revealed subtle differences in the structures between crystals derived from pure water and crystals derived from aqueous ethanol solutions. Finally, from the thermal analysis it was deduced that crystals obtained from pure water were stoichiometrically dihydrates whereas crystals obtained from aqueous ethanol solutions were 2.5 hydrates; this formation of different hydrates were supported by the Raman difference analysis.

  • 50.
    Enman, Josefine
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ramser, Kerstin
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Signals and Systems.
    Rova, Ulrika
    Berglund, Kris
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Raman analysis of synthetic eritadenine2008In: Journal of Raman Spectroscopy, ISSN 0377-0486, E-ISSN 1097-4555, Vol. 39, no 10, p. 1464-1468Article in journal (Refereed)
    Abstract [en]

    Eritadenine, 2(R),3(R)-dihydroxy-4-(9-adenyl)-butyric acid, is a cholesterol-reducing compound naturally occurring in the shitake mushroom (Lentinus edodes). To identify the unknown Raman spectrum of this compound, pure synthetic eritadenine was examined and the vibrational modes were assigned by following the synthesis pathway. This was accomplished by comparing the known spectra of the starting compounds adenine and D-ribose with the spectra of a synthesis intermediate, methyl 5-(6-Aminopurin-9H-9-yl)-2,3-O-isopropylidene-5-deoxy-β-D-ribofuranoside (MAIR) and eritadenine. In the Raman spectrum of eritadenine, a distinctive vibrational mode at 773 cm-1 was detected and ascribed to vibrations in the carbon chain, ν(C--C). A Raman line that arose at 1212 cm-1, both in the Raman spectrum of MAIR and eritadenine, was also assigned to ν(C--C). Additional Raman lines detected at 1526 and at 1583 cm-1 in the Raman spectrum of MAIR and eritadenine were assigned to ν(N--C) and a deformation of the purine ring structure. In these cases the vibrational modes are due to the linkage between adenine and the ribofuranoside moiety for MAIR, and between adenine and the carbon chain for eritadenine. This link is also the cause for the disappearance of adenine specific Raman lines in the spectrum of both MAIR and eritadenine. Several vibrations observed in the spectrum of D-ribose were not observed in the Raman spectrum of eritadenine due to the absence of the ribose ring structure. In the Raman spectrum of MAIR some of the D-ribose specific Raman lines disappeared due to the introduction of methyl and isopropylidene moieties to the ribose unit. With the approach presented in this study the so far unknown Raman spectrum of eritadenine could be successfully identified and is presented here for the first time.

12345 1 - 50 of 203
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf