| 1. |
- af Klinteberg, C, et al.
(author)
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Laser-induced fluorescence diagnostics of basal cell carcinomas of the skin following topical ALA application
- 1996
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In: Optical Biopsies and Microscopic Techniques, Proceedings of. - : SPIE. - 0819423289 ; 2926, s. 32-40
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Conference paper (peer-reviewed)abstract
- Fourteen patients with superficial basal cell carcinomas (BCCs) and fifteen patients with nodular BCCs were investigated by means of laser-induced fluorescence (LIF) in connection with photodynamic therapy (PDT). Topical application of delta-amino levulinic acid (ALA) was performed six hours prior to the treatment session. Fluorescence spectra were recorded, using a point-monitoring system with an excitation wavelength of 405 nm. The measurements were performed in scans over the lesion and the surrounding normal skin before application of ALA, and immediately before and after the laser treatment. The selective uptake of the photosensitiser resulted in a fluorescence intensity ratio of 2.4:1 for superficial BCCs and 2.5:1 for nodular BCCs. If the fluorescence intensity was divided by the autofluorescence, this resulted in a contrast enhancement of about a factor 6 for tumour tissue. In seven patients (five with nodular BCC and two with superficial BCC), additional fluorescence measurements were performed two and four hours following the ALA application, and two hours after the PDT procedure. Thus, the kinetics of the transformation of ACA to protoporphyrin IX (PpIX) could be followed, which indicated that the synthesis of PpIX was more rapid in the tumour than in the normal tissue. After four hours, the PpIX level inside the tumour was saturated, while there still was an accumulation in the surrounding skin. The highest contrast between tumour and normal skin was reached within two hours after the ALA application.
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| 2. |
- Nordström, Tomas, 1963-, et al.
(author)
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Using and designing massively parallel computers for artificial neural networks
- 1992
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In: Journal of Parallel and Distributed Computing. - Orlando : Academic Press. - 0743-7315 .- 1096-0848. ; 14:3, s. 260-285
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Journal article (peer-reviewed)abstract
- During the past 10 years the fields of artificial neural networks (ANNs) and massively parallel computing have been evolving rapidly. The authors study the attempts to make ANN algorithms run on massively parallel computers as well as designs of new parallel systems tuned for ANN computing. Following a brief survey of the most commonly used models, the different dimensions of parallelism in ANN computing are identified, and the possibilities for mapping onto the structures of different parallel architectures are analyzed. Different classes of parallel architectures used or designed for ANN are identified. Reported implementations are reviewed and discussed. It is concluded that the regularity of ANN computations suits SIMD architectures perfectly and that broadcast or ring communication can be very efficiently utilized. Bit-serial processing is very interesting for ANN, but hardware support for multiplication should be included. Future artificial neural systems for real-time applications will require flexible processing modules that can be put together to form MIMSIMD systems
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| 3. |
- Eklund, Anders, 1965-, et al.
(author)
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A catheter tactile sensor for measuring hardness of soft tissue : measurement in a silicone model and in an in vitro human prostate model
- 1999
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In: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 37:5, s. 618-624
-
Journal article (peer-reviewed)abstract
- 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
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| 4. |
- Brandberg, Joakim, et al.
(author)
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Increased accuracy of echocardiographic measurement of flow using automated spherical integration of multiple plane velocity vectors
- 1999
-
In: Ultrasound in Medicine and Biology. - 0301-5629 .- 1879-291X. ; 25:2, s. 249-257
-
Journal article (peer-reviewed)abstract
- The calculation of blood flow in the heart by surface integration of velocity vectors (SIVV) using Doppler ultrasound is independent of the angle. Flow is normally calculated from velocity in a spherical thick shell with its center located at the ultrasound transducer. In a numerical simulation, we have shown that the ratio between minor and major axes of an elliptic flow area substantially influences the accuracy of the estimation of flow in a single scan plane. The accuracy of flow measurements by SIVV can be improved by calculating the mean of the values from more than one scan plane. We have produced an automated computer program that includes an antialiasing procedure. We confirmed an improvement of flow measurements in a pulsatile hydraulic flow model, the 95% confidence interval for single estimations being reduced from 20% to 10% (p < 0.05) using the newly developed software. We think that the SIVV method has important implications for clinical transthoracic echocardiography.
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| 5. |
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| 6. |
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| 7. |
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| 8. |
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| 9. |
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| 10. |
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| 11. |
- Berbyuk, Viktor, 1953
(author)
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Multibody dynamics and optimization problems of an above-knee prostheses
- 1996
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Conference paper (other academic/artistic)abstract
- New prosthetic materials and designs have resulted in many prostheses of lower limbs which are presently available for the amputee to use. As a result, it is becoming more difficult for the prosthetists and the physicians to choose which prosthesis is the best for the individual amputee. Presently, there is limited information about how the prosthesis performs dynamically in achieving optimal symmetrical gait for amputee. To provide insight into the interaction between dynamics and control in biotechnical systems and for optimizing the prosthesis's structure the energy-optimal control problem of the human locomotor system (HLS) wearing an above-knee prosthesis has been considered. The algorithm based on multibody dynamics approach and special conversion of the optimal control problem for nonlinear dynamic system model of the HLS into a standard nonlinear programming problem has been proposed. A number of the energy-optimal control problems of human locomotion with an artificial leg and the optimization problems of the constructive parameters of an above-knee prostheses under different boundary conditions and constraints have been solved.
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| 12. |
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| 13. |
- Caidahl, Kenneth, 1949, et al.
(author)
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New concept in echocardiography: harmonic imaging of tissue without use of contrast agent.
- 1998
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In: Lancet (London, England). - : Elsevier BV. - 0140-6736. ; 352:9136, s. 1264-70
-
Journal article (peer-reviewed)abstract
- Endocardial border detection is important for echocardiographic assessment of left-ventricular function. Second harmonic imaging of contrast agents enhances this border detection. We discovered that harmonic imaging improves tissue visualisation even before contrast injection. We therefore sought objectively to demonstrate the degree of enhancement of endocardial and myocardial visualisation.An ATL HDI-3000 scanner with software for contrast harmonic imaging was used to record short-axis images of the left ventricle in 27 patients with possible myocardial disease and 22 controls, in the fundamental mode and with harmonic imaging. A computer program measured the relative grey-scale values within six segments of the endocardium and myocardium. An Acuson Sequoia scanner equipped with software for tissue harmonic imaging was used to investigate the reproducibility of ejection-fraction calculations in 22 patients with ischaemic heart disease.Harmonic imaging produced brighter endocardium within each segment. Relative to the mean grey value of the total imaging sector, the values for harmonic and fundamental imaging were 171.5 vs 85.6% (p<0.0001) in end diastole and 194.1 vs 106.7% (p<0.0001) in end systole. Results for the myocardial segments were also significantly better for harmonic imaging. Structure enhancement of similar magnitude was seen among patients and healthy controls. Use of harmonic imaging reduced the proportion of unacceptable images by 14-46% in different views and improved the reproducibility of biplane ejection-fraction measurements.In comparison with fundamental imaging, the relative endocardial and myocardial brightness is enhanced by harmonic imaging.
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| 14. |
- Gustafsson, Agnetha, et al.
(author)
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Evaluation of attenuation corrections using Monte Carlo simulated lung SPECT
- 1998
-
In: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 43:8, s. 2325-2336
-
Journal article (peer-reviewed)abstract
- SPECT (single photon emission computed tomography) images are distorted by photon attenuation. The effect is complex in the thoracic region due to different tissue densities. This study compares the effect on the image homogeneity of two different methods of attenuation correction in lung SPECT; one pre-processing and one post-processing method. This study also investigates the impact of attenuation correction parameters such as lung contour, body contour, density of the lung tissue and effective attenuation coefficient. The Monte Carlo technique was used to simulate SPECT studies of a digital thorax phantom containing a homogeneous activity distribution in the lung. Homogeneity in reconstructed images was calculated as the coefficient of variation (CV). The isolated effect of the attenuation correction was assessed by normalizing pixel values from the attenuation corrected lung by pixel values from the lung with no attenuation effects. Results show that the CV decreased from 12.8% with no attenuation correction to 4.4% using the post-processing method and true densities in the thoracic region. The impact of variations in the definition of the body contour was found to be marginal while the corresponding effect of variations in the lung contour was substantial
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| 15. |
- Anderson, C., et al.
(author)
-
Changes in skin circulation after microdialysis probe insertion visualized by laser Doppler perfusion imaging
- 1994
-
In: Journal of Investigative Dermatology. - 0022-202X .- 1523-1747. ; 102:5, s. 807-811
-
Journal article (peer-reviewed)abstract
- Microdialysis makes possible in vivo estimation of endogenous and exogenous substances in the dermal extracellular space. Insertion of the microdialysis probe and its subsequent presence in the skin may affect both the reactivity of the skin test site and the measurement of target substances. Laser Doppler flowmetry is a non-invasive method for estimating cutaneous blood flow. A further development of this technique, laser Doppler perfusion imaging, has been used to study the time course of the circulatory changes caused in the area of microdialysis probe insertion. Laser Doppler perfusion imaging was performed prior to, during, and after microdialysis probe insertion in the skin of the ventral forearm in three subjects. Probe insertion caused an increase in skin blood perfusion in the whole test area. About 15 min after probe insertion, the flare, which is presumed to be of chiefly axon reflex origin, began to subside and the circulatory response could be seen to center around the site of insertion and the tip of the probe. Skin perfusion levels had returned to near normal levels within 60 min. Local anesthesia of the point of guide insertion inhibited the flare, but did not affect circulatory reactivity in the skin nearby. Both microdialysis and laser Doppler perfusion imaging seem to be promising new methods in dermatologic research.
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| 16. |
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| 17. |
- Andersson, Mats, et al.
(author)
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Velocity Adaptive Filtered Angiography
- 1999
-
Patent (pop. science, debate, etc.)abstract
- A method of imaging a blood vessel in a body using X-rays and an injectable contrast medium is described. The contrast medium is injected into the body, and signals constituted by an X-ray image sequence depicting X-ray attenuation values is recorded. The X-ray attenuated values in each spaced-time neighborhood are combined in a way that is dependent on the processed image sequence and separately established for each neighborhood, and separating, from background and vessel signals, flow signals having energy contributions mainly in an area of frequency domain bounded by surfaces corresponding to threshold velocities separately established for each neighborhood, which surfaces are shifted a specified amount along a temporal frequency axis.
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| 18. |
- Andersson, T., et al.
(author)
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Human in vivo cutaneous microdialysis: Estimation of histamine release in cold urticaria.
- 1995
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In: Acta Dermato-Venereologica. - 0001-5555 .- 1651-2057. ; :75, s. 343-347
-
Journal article (peer-reviewed)abstract
- A novel bioanalytical in vivo sampling technique, cutaneous microdialysis, was used to follow the chronology of skin histamine release in 3 patients with cold urticaria and in 2 healthy volunteers. Laser Doppler perfusion imaging was used simultaneously to monitor the skin circulatory response. Microdialysis samples were collected at 10-min intervals and analysed by radioimmunoassay technique. Fifty minutes after probe insertion, the ventral forearm skin in the area of the dialysis membrane was provoked for 5-15 min with a 25 x 40 mm ice cube covered with plastic foil. In the cold urticaria patients, an up to 80-fold increase of histamine was observed, with peak levels 20-30 min after challenge. Histamine levels then fell to reach "baseline" levels within 50 min. In the healthy subjects, the histamine increase was earlier, less pronounced and of shorter duration. Cutaneous microdialysis and laser Doppler imaging offer new possibilities for the chronological multiparameter assessment of inflammatory skin disorders in vivo.
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| 19. |
- Borga, Magnus, et al.
(author)
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An Adaptive Stereo Algorithm Based on Canonial Correlation Analysis
- 1998
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In: Proceedings of the Second IEEE International Conference on Intelligent Processing Systems. ; , s. 177-182
-
Conference paper (peer-reviewed)abstract
- This paper presents a novel algorithm that uses CCA and phase analysis to detect the disparity in stereo images. The algorithm adapts filters in each local neighbourhood of the image in a way which maximizes the correlation between the filtered images. The adapted filters are then analysed to find the disparity. This is done by a simple phase analysis of the scalar product of the filters. The algorithm can even handle cases where the images have different scales. The algorithm can also handle depth discontinuities and give multiple depth estimates for semitransparent images.
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| 20. |
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| 21. |
- Hemmendorff, M., et al.
(author)
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Motion compensated digital subtraction angiography
- 1999
-
In: Proceedings of SPIE's International Symposium on Medical Imaging, vol 3661, 1999.
-
Conference paper (peer-reviewed)abstract
- Digital subtraction angiography, whether based on traditional X-ray or MR, suers from patient motion artifacts. Until now, the usual remedy is to pixel shift by hand, or in some cases performing a global pixel shift semi-automatically. This is time consuming, and cannot handle rotations or local varying deformations over the image. We have developed a fully automatic algorithm that provides for motion compensation in the presence of large local deformations. Our motion compensation is very accurate for ordinary motions, including large rotations and deformations. It does not matter if the motions are irregular over time. For most images, it takes about a second per image to get adequate accuracy. The method is based on using the phase from lter banks of quadrature lters tuned in dierent directions and frequencies. Unlike traditional methods for optical ow and correlation, our method is more accurate and less susceptible to disturbing changes in the image, e.g. a moving contrast bolus. The implications for common practice are that radiologists' time can be significantly reduced in ordinary peripheral angiographies and that the number of retakes due to large or local motion artifacts will be much reduced.
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| 22. |
- Janerot-Sjöberg, Birgitta, et al.
(author)
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Quantitative digital evaluation of myocardial exercise thallium-201 single-photon emission tomography in post-menopausal women
- 1998
-
In: Clinical Physiology. - : Wiley. - 0144-5979 .- 1365-2281. ; 18:3, s. 169-177
-
Journal article (peer-reviewed)abstract
- Quantitative computerized analysis of data from myocardial thallium-201 (201Tl) single-photon emission tomography (SPET) may improve the diagnostic accuracy of coronary heart disease. The reference ranges for post-menopausal women are, however, limited and obtained mainly from patients. To compare reference values from healthy post-menopausal women and to improve the quantitative analysis, 20 women (10 patients with coronary heart disease and previous infarction and 10 age-matched healthy volunteers) were examined immediately post exercise and after a delay. A nine-segment 'bull's-eye' model was used for analysis. At visual evaluation, reproducibility was high (93%), no false-positive results were obtained and in 70% of the patients the SPET was interpreted as abnormal. Using reported reference values for quantitative analysis, all the healthy women had an abnormal result. New reference values based on three different methods of 'normalization' were calculated: the relative activity of segment 3 set to 100%, the segment with the highest activity set to 100% and a least-squares method. They all differed significantly from those that had previously been reported. The frequencies of agreement between visual and quantitative analysis were 84-92% and were highest when segment 3 was used as a reference, but in this case only 40% of the patients with coronary heart disease had an abnormal SPET. Using the least-squares method for handling digital information, the SD of the normal values decreased and 90% of the patients with coronary heart disease were accurately diagnosed. These results provide quantitative digital reference values for healthy post-menopausal women. They verify that quantitative analysis is in diagnostic agreement with visual evaluation, stress the need for local verification of reference ranges and suggest a least-square normalization method for the analysis.
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| 23. |
- Rovai, Daniele, et al.
(author)
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Myocardial perfusion abnormalities by intravenous administration of the contrast agent NC100100 in an experimental model of coronary artery occlusion and reperfusion
- 1998
-
In: Echocardiography. - : Wiley. - 0742-2822 .- 1540-8175. ; 15:8, s. 731-740
-
Journal article (peer-reviewed)abstract
- The aim of this study was to evaluate a second-generation echo contrast agent (NC100100) for the study of myocardial perfusion. In eight anesthetized open-chest dogs, this agent was injected intravenously under baseline conditions, during acute coronary thrombosis, and after reperfusion, using both fundamental (FI) and harmonic (HI) imaging, both continuous and intermittent imaging, and both ultrasound (US) and integrated backscatter (IBS) imaging. Contrast injections did not modify the hemodynamic parameters. With all imaging modalities, myocardial contrast enhancement (MCE) was higher with intermittent than with continuous imaging (134 vs 82 gray level/pixel using FI, P = 0.02; 62 vs 32 acoustic units using US HI, P = 0.02; and 52 vs 12 dB using IBS, P = 0.05). MCE equally increased using either US or IBS imaging. The accuracy of MCE in detecting perfusion defects during coronary occlusion and myocardial reperfusion after thrombolysis was very good (sensitivity and specificity = 93% and 95% and 89% and 93%, respectively). The extent of myocardial perfusion defects by echo contrast showed a closer correlation with microspheres using HI (r = 0.82) than FI (r = 0.53). Thus, the intravenous administration of NC100100 during intermittent HI allows myocardial perfusion abnormalities to be accurately detected during acute myocardial infarction.
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| 24. |
- Troilius, A., et al.
(author)
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Evaluation of Portwine Stain Perfusion by Laser Doppler Imaging and Thermography Before and After Argon Laser Treatment
- 1992
-
In: Acta Dermato-Venereologica. - 0001-5555. ; 72:1, s. 6-10
-
Journal article (peer-reviewed)abstract
- Thirteen patients with port wine stains (PWS) were treated with argon laser therapy. Before and at different points in time following treatment, skin blood perfusion and temperature were mapped with laser Doppler imaging and thermography. In nine patients no elevation in blood perfusion was observed in the PWS in comparison with the surrounding normal skin before treatment. In the remaining four patients a significantly (p less than 0.01) higher blood flow was recorded within the PWS. Immediately after treatment nine patients showed elevated perfusion within the PWS. During the first two days following treatment, all patients showed a gradually decreasing hyperperfusion in the borderline between the PWS lesion and surrounding skin. Immediately after treatment 10 patients had a significantly (p less than 0.01) higher temperature in the PWS than in normal skin. During the first 24 h following treatment, an elevated perfusion was in general accompanied by a tissue temperature increase. Three and a half months after argon laser treatment, three patients showed excellent clinical results with no remaining PWS spots or scarring. Two of these patients had had both elevated perfusion and temperature in the PWS prior to treatment.
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| 25. |
- Wang, L., et al.
(author)
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Superficial Blood flow Following Photodynamic Therapy of Malignant Skin Tumours Measured by Laser Doppler Perfusion Imaging
- 1997
-
In: British Journal of Dermatology. - : Oxford University Press (OUP). - 0007-0963 .- 1365-2133. ; 136:2, s. 184-189
-
Journal article (peer-reviewed)abstract
- Laser Doppler perfusion imaging offers a new modality for in vivo monitoring of the superficial blood perfusion in biological tissue. In this study, the superficial blood perfusion of malignant nonmelanoma skin tumours and the surrounding normal skin was measured in conjunction with photodynamic therapy (PDT) using topical ò–aminolaevulinic acid (ALA)–induced protoporphyrin IX as a photosensitizer. The results clearly show that, in contradiction to PDT with the intravenously administered photosensitizer photofrin. no direct vascular damage can be seen. With the topical sensitization the blood perfusion is increased immediately after the treatment irradiation. The increased blood flow is seen up to a week after treatment, in a similiar way as for an inflammatory reaction. Despite this, all basal cell carcinoma and squamous cell carcinoma in situ lesions in this study healed without any sign of residual tumour after the treatment, suggesting an efficient direct tumour cell destruction induced by PDT.
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| 26. |
- Wilkenshoff, Ursula M., et al.
(author)
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Regional mean systolic myocardial velocity estimation by real-time color Doppler Myocardial Imaging: A new technique for quantifying regional systolic function
- 1998
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In: Journal of the American Society of Echocardiography. - : Elsevier BV. - 0894-7317 .- 1097-6795. ; 11:7, s. 683-692
-
Journal article (peer-reviewed)abstract
- A new color Doppler myocardial imaging (CDMI) system with high spatial and temporal resolution and novel postprocessing modalities has been developed that could allow quantifiable stress echocardiography. The purpose of this study was to determine whether regional myocardial systolic velocities could be accurately and reproducibly measured both at rest and during bicycle ergometry by using CDMI. Thirty normal subjects were examined with CDMI at rest, and peak mean systolic myocardial velocities (MSV) were measured for 34 predetermined left ventricular myocardial segments. Interobserver variability and intraobserver variability were established for all segments. Submaximal bicycle ergometry was performed in 20 normal subjects by using standardized weight-related increases in workload. MSV were measured at each step of exercise for 16 left ventricular stress echo segments. At rest, a base-apex gradient in regional MSV was recorded with highest longitudinal shortening velocities at the base. A similar pattern was noted for circumferential shortening MSV. Measurements were predictable and highly reproducible with low interobserver and intraobserver variability for 26 of 34 segments. Reproducibility was poor for basal anteroseptal segments in all views and mid anterior, anteroseptal, and septal segments in the short-axis views. During exercise, mid and basal segments of all walls showed a significant increase of MSV between each workload step and for apical segments between alternate steps. The resting base-apex velocity gradient observed at rest remained in all walls throughout ergometry. Thus a CDMI system with improved spatial and temporal resolution and postprocessing analysis modalities provided reproducible and accurate quantification of segmental left ventricular circumferential and longitudinal contraction both at rest and during exercise.
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| 27. |
- Wårdell, Karin, et al.
(author)
-
Laser Doppler Perfusion Imaging by Dynamic Light Scattering
- 1993
-
In: IEEE Transactions on Biomedical Engineering. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9294 .- 1558-2531. ; 40:4, s. 309-316
-
Journal article (peer-reviewed)abstract
- A laser Doppler perfusion imaging technique based on dynamic light scattering in tissue is reported. When a laser beam sequentially scans the tissue (maximal area approximately 12 cm*12 cm), moving blood cells generate Doppler components in the backscattered light. A fraction of this light is detected by a remote photodiode and converted into an electrical signal. In the signal processor, a signal proportional to the tissue perfusion at each measurement point is calculated and stored. When the scanning procedure is completed, the system generates a color-coded perfusion image on a monitor. A perfusion image is typically built up of data from 4096 measurement sites, recorded during a time period of 4 min. This image has a spatial resolution of about 2 mm. A theory for the system inherent amplification factor dependence on the distance between individual measurement points and detector is proposed and correction measures are presented. Performance results for the laser Doppler perfusion imager obtained with a flow simulator are presented. The advantages of the method are discussed.
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| 28. |
- Wårdell, Karin, et al.
(author)
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Spatial heterogeity in normal skin perfusion recorded with laser Doppler imaging and flowmetry
- 1994
-
In: Microvascular Research. - 0026-2862 .- 1095-9319. ; 48:1, s. 26-38
-
Journal article (peer-reviewed)abstract
- Spatial and temporal variations in forearm skin perfusion captured by laser Doppler perfusion imaging (LDI) have been compared with topographic maps recorded by laser Doppler flowmetry. In order to determine the shortest LDI sampling time required at each measurement site, with an adequate signal-to-noise ratio and with the ability to display the heterogeneity in skin perfusion, the noise-limited resolution of the LDI system as well as various sampling times were tested. The noise-limited resolution for medium and high light intensities were less than 0.5% (temporal) and 0.3% (spatial) of full scale. A sampling time of 1 sec was selected and image presentation was made by performing bilinear interpolation between perfusion values. The same area (10 x 10 mm) was mapped with LDI and topographic mapping at seven different sites. In addition, a larger area covering the surrounding skin was recorded with LDI. The small area recordings with LDI and topographic mapping could be identified in the larger LDI image. High-and low-perfusion spots coincided between the two systems. Temporal variations were studied by repeated LDI recordings of the same areas as above. Small spots were selected in the areas and plotted versus time. Without provocation, the total perfusion changes at each spot showed large variations, but the relative perfusion levels between neighboring spots persisted. Provocation with heat increased the perfusion in all spots.
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| 29. |
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| 30. |
- Verikas, Antanas, 1951-, et al.
(author)
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Hierarchical neural network for color classification
- 1994
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In: The 1994 IEEE International Conference on Neural Networks. - Piscataway, NJ : IEEE Press. - 078031901X ; , s. 2938-2941
-
Conference paper (peer-reviewed)abstract
- To make the hierarchical architecture, the neural networks of different type and different unsupervised learning techniques were combined. The classification accuracy obtained from such architecture is high enough to use it in the print quality control.
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Fröjse, Rolf, et al.
(author)
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A new method for continuous tonometric pCO2 measurement : in vitro studies
- 1999
-
In: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 20:2, s. 129-136
-
Journal article (peer-reviewed)abstract
- The available methods for tonometric pCO2 measurement only provide the possibility of performing intermittent registrations. A new method allowing continuous tonometric pCO2 measurement has been developed and tested in an in vitro model. A standard tonometer for intestinal pCO2 measurement was modified to allow continuous perfusion of the balloon with physiological saline solution in a closed system. The pCO2 in the system was determined in a specially sructed measurement chamber with a TCM20 percutaneous pCO2 monitor. In this in vitro model the tonometer balloon was placed in a saline bath with a constant pCO2 concentration and the measurements from the closed circulating system were compared with those obtained from a standard tonometer placed in the same bath. In 8 and 24 h experiments the circulating system measured the pCO2 value as accurately and reliably as traditional tonometry. This study indicates that the new method makes continuous monitoring of pCO2 possible
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| 36. |
- Lindahl, Olof, et al.
(author)
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A tactile sensor for detection of physical properties of human skin in vivo
- 1998
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In: Journal of Medical Engineering & Technology. - : Informa UK Limited. - 0309-1902 .- 1464-522X. ; 22:4, s. 147-153
-
Journal article (peer-reviewed)abstract
- A spring loaded tactile sensor with displacement sensing has been evaluated for non-invasive assessment of physical properties, stiffness and elasticity, of human skin in vivo. The tactile sensor consists of a peizoelectric vibrator (61 kHz) with a vibration pickup, electronics and PC with software for measurement of the change in frequency when the sensor is attached to an object. Integrated with the tactile sensor is a displacement sensor that shows the compression of the spring that loads the sensor element against the object during measurement. Under certain conditions (e.g. fixed contact pressure) this change in frequency monitors the acoustic impedance of the object and is related to the stiffness of soft tissue. The experimental results on silicone gum and on healthy Japanese and Swedish women indicated that the instrument was able to detect changes in stiffness and elastic related properties of human skin, related to age, day-to-day variations and application of cosmetics. The instrument was concluded to be easy to handle and suitable for field work
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| 37. |
- Lindahl, Olof, et al.
(author)
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An electromechanical breathing device for minimal particle loss while inhaling aerosols
- 1993
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In: Journal of Medical Engineering & Technology. - : Informa UK Limited. - 0309-1902 .- 1464-522X. ; 17:4, s. 138-140
-
Journal article (peer-reviewed)abstract
- The design of an electromechanical breathing mask that minimizes particle loss during inhalation of aerosols from a provocation box is described. The device measures air flow by means of an anemometer. A provocation example is depicted and the possibility of measuring the provocation dose is discussed. The breathing device here described has been shown to be easy to use and to give reliable results
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| 38. |
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| 39. |
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| 40. |
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| 41. |
- Lindahl, Olof, et al.
(author)
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Evaluation of the impression technique by measuring interstitial oedema in rat testis
- 1991
-
In: Acta Physiologica Scandinavica. - : Wiley. - 0001-6772 .- 1365-201X. ; 143:3, s. 255-260
-
Journal article (peer-reviewed)abstract
- The impression method for assessment of subcutaneous oedema was evaluated in a rat testis model where the testicular interstitial fluid volume was changed both artificially by infusion of rat plasma and pharmacologically by administration of human chorionic gonadotrophin. Both the integral value and the impression force value, as measured with the impression method, changed with infused volume, and changes as small as 16 microliters (approximately 7% of the total interstitial fluid volume in a testis) could be detected. Rats were treated with a single injection of 100 i.u. human chorionic gonadotrophin in order to induce changes in the volume of interstitial fluid in the testis. Both the integral value and the impression force value seemed to reveal information on testicular interstitial fluid volume in rats treated with human chorionic gonadotrophin that was similar to data revealed by measuring the actual fluid content in the testis. Interstitial fluid volume measured morphometrically in the contralateral testis in human chorionic gonadotrophin-treated rats was significantly correlated to the impression force value (r = 0.75) and the integral value (r = 0.52). This rat testis model proved to be an interesting experimental set-up for evaluation of the impression technique.
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| 42. |
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| 43. |
- Lindahl, Olof, et al.
(author)
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Grip strength of the human hand : measurements on normal subjects with a new hand strength analysis system (Hastras)
- 1994
-
In: Journal of Medical Engineering & Technology. - : Informa UK Limited. - 0309-1902 .- 1464-522X. ; 18:3, s. 101-103
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Journal article (peer-reviewed)abstract
- This study describes a method of acquiring data from healthy and non-injured men that can be used as reference data when measuring the grip strength of the human hand using newly developed, PC-based hand strength analysis equipment--'Hastras'. Hastras can be used for continuous measurement and recording of force when the subject grips a sensor with maximum power. Computerized analysis of the force signal gives information about maximum force, fatigue, area and rise (force/s). The statistical analysis of the measurements on 81 subjects are consistent with earlier published data from other hand strength equipment. It is concluded that Hastras gives easy processing and storage of data, and also a detailed analysis of grip function.
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| 44. |
- Lindahl, Olof, et al.
(author)
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Human postburn oedema measured with the impression method
- 1993
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In: Burns. - 0305-4179 .- 1879-1409. ; 19:6, s. 479-484
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Journal article (peer-reviewed)abstract
- The course of tissue swelling in human non-injured skin after burn injury was investigated with a non-invasive impression method that measures force and tissue fluid translocation during mechanical compression of the skin. Time-dependent changes in the fluid translocation and the interstitial-pressure related to impression force were measured on 11 occasions, during 3 weeks, in seven patients postburn. A mathematical model was fitted to the impression force curves and the parameters of the model depicted the time-dependent compartmental fluid shift in the postburn generalized oedema. Tissue fluid translocation increased significantly (P < 0.05) up to a maximum value after 6 days postburn and declined thereafter. This indicated a continuous increase in the generalized postburn oedema for the first 6 days postburn. Impression force at 3 weeks postburn was significantly lower (P < 0.001) as compared with the half-day postburn value, indicating an increased tissue pressure during the first days postburn. Parameter analysis indicated a flux of water-like fluid from the vasculature to the interstitial space during the first 6 days postburn. The spread of the values registered between different measurement sites was, however, large.
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| 45. |
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| 46. |
- Lindahl, Olof, et al.
(author)
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Impression technique for the assessment of oedema : comparison with a new tactile sensor that measures physical properties of tissue
- 1995
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In: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 33:1, s. 27-32
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Journal article (peer-reviewed)abstract
- To measure tissue oedema, the impression technique and a new tactile sensor technique are compared and evaluated in a silicone rubber model and in an in vivo rat testis model. The principles of the two techniques differ in that the impression technique evaluates interstitial fluid flow FT and peak force F(O) when tissue is compressed, whereas the tactile sensor evaluates the hardness/softness or change in resonance frequency delta f when a vibrating rod is attached to tissue. Both techniques can detect changes in silicone hardness/softness or in hormone-induced changes of testis interstitial fluid. Although both F(O) and FT are significantly correlated to delta f in the experiments, it is concluded that F(O) is the most promising impression parameter to give valuable information about the hardness of living tissue as compared with delta f. The comparison indicates that the impression technique is the most easy to interpret, non-invasive tool to assess tissue oedema so far developed.
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| 47. |
- Lindahl, Olof, et al.
(author)
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Impression technique for the assessment of oedema : technical improvement and methodological evaluation of a new technique
- 1991
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In: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 29:6, s. 591-597
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Journal article (peer-reviewed)abstract
- A new instrument for the assessment of oedema based on the impression method is described. The measurement parameters are defined and the errors corresponding to the electrical and mechanical stability of the instrument are measured. The overall accuracy is calculated theoretically for the translocated volume. The accuracy and reproducibility are evaluated on plastic foam. The clinical procedure to measure oedema with this instrument is described. We show that the accuracy of the translocated volume parameter is very dependent on the overall stability of the instrument and that this instrument has an overall relative error of less than 7.3 per cent for a representative measurement. Experimental measurements on plastic foam show that the measurement parameters could be reproduced with standard deviations of less than 6 per cent and that the standard deviations for translocated volume are within the calculated overall relative error. Measurements on four patients with chronic oedema in an extremity show significantly different results on locations where pitting could be recognised compared to the contralateral nonoedematous extremity.
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| 48. |
- Lindahl, Olof, et al.
(author)
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Impressionsmedtoden för bedömning av ödem
- 1990
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In: STU-seminarium i biomedicinsk mätteknik, Uppsala 1990. - : Styrelsen för teknisk utveckling.
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Conference paper (other academic/artistic)
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| 49. |
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| 50. |
- Lindahl, Olof, et al.
(author)
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Impressionsmetoden för bedömning av ödem
- 1991
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In: STU-seminarium i biomedicinsk mätteknik, Huddinge 1991. - : Styrelsen för teknisk utveckling.
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Conference paper (other academic/artistic)
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