maryamam

• Tronstad, Christian; Amini, Maryam; Olesen, Eline; Qvigstad, Elisabeth; Pabst, Oliver & Martinsen, Tormod [Show all 11 contributors for this article] (2022). Diabetic foot assessment using skin impedance in a custom made sensor-sock. Journal of Electrical Bioimpedance. 13(1), p. 136–142. doi: 10.2478/joeb-2022-0019. Full text in Research Archive Show summary

  Abstract Diabetic peripheral neuropathy (DPN) may lead to several changes in the skin, and some of these may influence the skin impedance spectrum. In the present study we have developed a prototype solution for skin impedance spectroscopy at selected skin sites (big toe pulp, heel and toe ball) that was tested in a pilot study on five patients with DPN and five healthy controls. At the big toe, most of the controls had markedly lower impedance than the DPN group, especially in the range of 1-100 kHz. The separation between the groups seems to be weaker at the heel and weakest at the toeball. The results may indicate that monitoring of the skin impedance spectrum may be a method for detection of skin changes associated with DPN, encouraging further studies with the big toe sensor in particular.

• Tronstad, Christian; Amini, Maryam; Bach, Dominik R. & Martinsen, Ørjan Grøttem (2022). Current trends and opportunities in the methodology of electrodermal activity measurement. Physiological Measurement. ISSN 0967-3334. 43(2). doi: 10.1088/1361-6579/ac5007. Full text in Research Archive
• Tronstad, Christian; Pabst, Oliver; Amini, Maryam; Kleggetveit, Inge Petter; Elvebakk, Ole & Martinsen, Ørjan Grøttem [Show all 10 contributors for this article] (2022). Development of a prototype toe sensor for detection of diabetic peripheral small fiber neuropathy. Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC). doi: 10.1109/EMBC48229.2022.9871101. Full text in Research Archive
• Amini, Maryam; Niemi, Essi Maria; Hisdal, Jonny; Kalvøy, Håvard; Tronstad, Christian & Scholz, Hanne [Show all 8 contributors for this article] (2020). Monitoring the quality of frozen-thawed venous segments using bioimpedance spectroscopy. Physiological Measurement. ISSN 0967-3334. 41(4). doi: 10.1088/1361-6579/ab85b7. Full text in Research Archive Show summary

  Objective: Storage at temperatures as low as −80 °C and below (cryopreservation) is considered a method for long-term preservation of cells and tissues, and especially blood vessel segments, which are to be used for clinical operations such as transplantation. However, the freezing and thawing processes themselves can induce injuries to the cells and tissue by damaging the structure and consequently functionality of the cryopreserved tissue. In addition, the level of damage is dependent on the rate of cooling and warming used during the freezing-thawing process. Current methods for monitoring the viability and integrity of cells and tissues after going through the freezing-thawing cycle are usually invasive and destructive to the cells and tissues. Therefore, employing monitoring methods which are not destructive to the cryopreserved tissues, such as bioimpedance measurement techniques, is necessary. In this study we aimed to design a bioimpedance measurement setup to detect changes in venous segments after freezing-thawing cycles in a noninvasive manner. Approach: A bioimpedance spectroscopy measurement technique with a two-electrode setup was employed to monitor ovine jugular vein segments after each cycle during a process of seven freezing-thawing cycles. Main results: The results demonstrated changes in the impedance spectra of the measured venous segments after each freezing-thawing cycle. Significance: This indicates that bioimpedance spectroscopy has the potential to be developed into a novel method for non-invasive and non-destructive monitoring of the viability of complex tissue after cryopreservation.

• Amini, Maryam; Kalvøy, Håvard & Martinsen, Ørjan Grøttem (2020). Finite element simulation of the impedance response of a vascular segment as a function of changes in electrode configuration. Journal of Electrical Bioimpedance. 11(1), p. 112–131. doi: 10.2478/JOEB-2020-0017. Full text in Research Archive Show summary

  Abstract Monitoring a biological tissue as a three dimensional (3D) model is of high importance. Both the measurement technique and the measuring electrode play substantial roles in providing accurate 3D measurements. Bioimpedance spectroscopy has proven to be a noninvasive method providing the possibility of monitoring a 3D construct in a real time manner. On the other hand, advances in electrode fabrication has made it possible to use flexible electrodes with different configurations, which makes 3D measurements possible. However, designing an experimental measurement set-up for monitoring a 3D construct can be costly and time consuming and would require many tissue models. Finite element modeling methods provide a simple alternative for studying the performance of the electrode and the measurement set-up before starting with the experimental measurements. Therefore, in this study we employed the COMSOL Multiphysics finite element modeling method for simulating the effects of changing the electrode configuration on the impedance spectroscopy measurements of a venous segment. For this purpose, the simulations were performed for models with different electrode configurations. The simulation results provided us with the possibility of finding the optimal electrode configuration including the geometry, number and dimensions of the electrodes, which can be later employed in the experimental measurement set-up.

• Amini, Maryam; Hisdal, Jonny; Rosales, Antonio; Kalvøy, Håvard & Martinsen, Ørjan Grøttem (2020). Evaluating the Effects of Cold Storage on Vascular Grafts Using Bioimpedance Measurement Techniques. International Federation for Medical and Biological Engineering Proceedings. ISSN 1680-0737. p. 127–132. doi: 10.1007/978-981-13-3498-6_19. Full text in Research Archive
• Amini, Maryam; Hisdal, Jonny & Kalvøy, Håvard (2018). Applications of bioimpedance measurement techniques in tissue engineering. Journal of Electrical Bioimpedance. 9(1), p. 142–158. doi: 10.2478/joeb-2018-0019. Full text in Research Archive Show summary

  Rapid development in the field of tissue engineering necessitates implementation of monitoring methods for evaluation of the viability and characteristics of the cell cultures in a real-time, non-invasive and non-destructive manner. Current monitoring techniques are mainly histological and require labeling and involve destructive tests to characterize cell cultures. Bioimpedance measurement technique which benefits from measurement of electrical properties of the biological tissues, offers a non-invasive, label-free and real-time solution for monitoring tissue engineered constructs. This review outlines the fundamentals of bioimpedance, as well as electrical properties of the biological tissues, different types of cell culture constructs and possible electrode configuration set ups for performing bioimpedance measurements on these cell cultures. In addition, various bioimpedance measurement techniques and their applications in the field of tissue engineering are discussed.

• Amini, Maryam; Hisdal, Jonny; Gjøvaag, Terje; Kapetanovic, Nihad; Strand, Trond-Eirik & Owe, Jan Ove [Show all 8 contributors for this article] (2016). Near-Infrared Spectra in Buccal Tissue as a Marker for Detection of Hypoxia. Aerospace Medicine and Human Performance. ISSN 2375-6314. 87(5), p. 498–504. doi: 10.3357/AMHP.4510.2016. Full text in Research Archive Show summary

  Abstract: INTRODUCTION: Hypoxia caused by high altitude exposure can impair cerebral and mental functions. Blood flow and oxygenation of the buccal tissue can be reliable markers to detect hypoxia. In this study, near infrared spectroscopy was used in combination with a novel optical probe to evaluate the applicability of the novel probe in measuring hypoxia markers in buccal tissue under a hypoxic condition. METHODS: Six healthy participants were tested at altitudes from 2000 to 16,000 ft inside a hypobaric chamber. The buccal reference measurements of blood flow and oxygen saturation were synchronized with the spectral measurements of the novel near infrared probe and the relationship between the reference measurements and spectral data were evaluated by multivariate partial least square method. In addition, finger oxygen saturation was measured during the experiment and the recordings were compared with buccal oxygen saturation. RESULTS: The spectral analysis illustrated that the spectral data from the near infrared probe correlated strongly with the absorption features of both buccal flow and oxygenation measured by the reflectance sensors (average R2 = 0.89). The results showed probably overestimated values for buccal oxygen saturation recorded by the reference pulse oximeter in comparison with finger oxygen saturation, with the mean difference increasing from 1.8% at 2000 ft to 11.4% at 16,000 ft. CONCLUSION: The novel near infrared probe showed promising results for simultaneous measurement of blood flow and oxygen saturation in the buccal tissue. The suggested method can be used as a new technique for early indication of hypoxia in future clinical applications.

• Amini, Maryam; Gjøvaag, Terje; Hisdal, Jonny & Mirtaheri, Peyman (2011). A Novel Design of an Optical Probe for Detecting Perfusion Changes in Buccal Tissue. IEEE Sensors Journal. ISSN 1530-437X. PP(99). doi: 10.1109/JSEN.2011.2177082. Full text in Research Archive Show summary

  Measuring the blood perfusion and microcirculation at a specific depth in human tissue is an important method to monitor oxygenation in critically ill patients. The optical probes that are currently available in the market are not capable of monitoring the blood perfusion from a given tissue layer and at a specific depth. We have designed a novel optical probe which is able to focus the light at a specific depth of ~ 670 ìm in buccal tissue. The new probe consists of two light guides for sending and detecting the reflected light from the sampling area (tissue), and a lens to focus the light into the desired depth of the tissue and collect it back from the same area. The new optical probe has been compared to a commercial laser Doppler probe by collecting data from the same sampling area. The result from our probe showed 15% higher accuracy in detecting changes in blood perfusion compared with an existing commercial probe.

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