| 1. |
- Jonsson, Thomas B., 1971-, et al.
(författare)
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Adverse events during treatment limb ischemia with autologous peripheral blood mononuclear cell implant
- 2012
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Ingår i: International Journal of Angiology. - Turin, Italy : Edizioni Minerva Medica. - 0392-9590 .- 1827-1839. ; 31:1, s. 77-84
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Tidskriftsartikel (refereegranskat)abstract
- Aim: Trials have reported clinical improvement and reduced need for amputation in critical limb ischemia (CLI) patients receiving therapeutic angiogenesis with stem cells. Our objective was to test peripheral stem cell therapy efficacy and safety to gain experiences for further work.Methods: We included nine CLI patients (mean age 76.7 ±9.7). Stem cells were mobilized to the peripheral blood by administration of G-CSF (Filgrastim) for 4 days, and were collected on day five, when 30 mL of a stem cell suspension was injected into 40 points of the limb. The clinical efficacy was evaluated by assessing pain relief, wound healing and changes in ankle-brachial pressure index (ABI). Local metabolic and inflammatory changes were measured with microdialysis, growth factors and cytokine level determination. Patients were followed for 24 weeks.Results: Four patients experienced some degree of improvement with pain relief and/or improved wound healing and ABI increase. One patient was lost to follow up due to chronic psychiatric illness; one was amputated after two weeks. Two patients had a myocardial infarction (MI), one died. One patient died from a massive mesenteric thrombosis after two weeks and one died from heart failure at week 11. Improved patients showed variable effects in cytokine-, growth factor- and local metabolic response.Conclusion: Even with some improvement in four patients, severe complications in four out of nine patients, and two in relation to the bone marrow stimulation, made us terminate the study prematurely. We conclude that with the increased risk and the reduced potential of the treatment, peripheral blood stem cell treatment in the older age group is less appropriate. Metabolic and inflammatory response may be of value to gain insight into mechanisms and possibly to evaluate effects of therapeutic angiogenesis.
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| 2. |
- 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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| 3. |
- 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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| 4. |
- Jonsson, Ulf G., 1950-, et al.
(författare)
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Investigations Of The Low And High Frequency Response Of 3ω-Sensors Used In Dynamic Heat Capacity Measurements
- 1998
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Ingår i: Measurement science and technology. - London : Institute of Physics. - 0957-0233 .- 1361-6501. ; 9:11, s. 1873-1885
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Tidskriftsartikel (refereegranskat)abstract
- The 3ω-method is used to study time dependent processes through measurements of dynamic heat capacity. The 3ω-sensor is a thin (∼ 0.1 μm) metal strip which is evaporated onto a substrate. The sample is probed by periodic diffusive thermal waves of frequency 2ω emitted from the strip. The heater temperature T0 measured at frequency 3ω yields the dynamic heat capacity. The validity of a one-dimensional heat flow model, assuming an infinitely thin heater, is here studied using a finite element modelling (FEM) technique as well as experiments. To obtain results within 1% of the theory, FEM shows that the ratio between the heater width and the heat wave penetration depth (=√D/ω, where D is the thermal diffusivity) must be greater than 30, which sets a low-frequency limit for the model. At high frequencies, the finite thickness of the heater causes a deviation from the model. For a thickness of 0.1 μm, the deviation is <1% at 200 Hz, reaching 5% at 5 kHz. A small 3ω-component intrinsic to the electronics together with a thermal resistance between heater and sample can explain deviations from T0 ∝ ω-υ, at high frequencies, where υ = 0.5 is predicted by the model but experiments generally show smaller values.
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