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- Eklund, Anders, et al.
(författare)
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Evaluation of applanation resonator sensors for intra-ocular pressure measurement : results from clinical and in vitro studies.
- 2003
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Ingår i: Medical and Biological Engineering and Computing. - 0140-0118 .- 1741-0444. ; 41:2, s. 190-197
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Tidskriftsartikel (refereegranskat)abstract
- Glaucoma is an eye disease that, in its most common form, is characterised by high intra-ocular pressure (IOP), reduced visual field and optic nerve damage. For diagnostic purposes and for follow-up after treatment, it is important to have simple and reliable methods for measuring IOP. Recently, an applanation resonator sensor (ARS) for measuring IOP was introduced and evaluated using an in vitro pig-eye model. In the present study, the first clinical evaluation of the same probe has been carried out, with experiments in vivo on human eyes. There was a low but significant correlation between IOP(ARS) and the IOP measured with a Goldmann applanation tonometer (r = 0.40, p = 0.001, n = 72). However, off-centre positioning of the sensor against the cornea caused a non-negligible source of error. The sensor probe was redesigned to have a spherical, instead of flat, contact surface against the eye and was evaluated in the in vitro model. The new probe showed reduced sensitivity to off-centre positioning, with a decrease in relative deviation from 89% to 11% (1 mm radius). For normalised data, linear regression between IOP(ARS) and direct IOP measurement in the vitreous chamber showed a correlation of r = 0.97 (p < 0.001, n = 108) and a standard deviation for the residuals of SD < or = 2.18 mm Hg (n = 108). It was concluded that a spherical contact surface should be preferred and that further development towards a clinical instrument should focus on probe design and signal analysis.
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| 2. |
- Munthe, Christian, 1962
(författare)
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Etiska aspekter på regenerativ medicin : Ethical aspects on regenerative medicine
- 2003
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Ingår i: SNIB-konferensen 2003, Chalmers tekniska högskola, Göteborg, 16-18 maj 2003.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Inom den regenerativa medicinen strävar man efter att ersätta skadat eller sjukligt biologiskt mänskligt material (celler, organ, kroppsdelar) med nya biologiska komponenter. Området aktualiserar en rad etiska frågeställningar vad gäller (1) produktionen av ersättningsmaterialet (t.ex. embryonala stamceller eller införskaffande av transplantationsvävnad från donatorer), (2) risker i samband med försök på människa (genmodifierat material, material från djur), samt (3) gränserna för hur långt man bör gå i denna slags försök att förlänga människans livsspann. Föredraget ger en kort översikt över dessa frågeställningar, ståndpunkter och argument i debatten kring dem.
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| 5. |
- Chew, Michelle, et al.
(författare)
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Pediatric cardiac output measurement using surface integration of velocity vectors : an in vivo validation study
- 2000
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Ingår i: Critical Care Medicine. - : Ovid Technologies (Wolters Kluwer Health). - 0090-3493 .- 1530-0293. ; 28:11, s. 3664-3671
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Tidskriftsartikel (refereegranskat)abstract
- Objective: To test the accuracy and reproducibility of systemic cardiac output (CO) measurements using surface integration of velocity vectors (SIVV) in a pediatric animal model with hemodynamic instability and to compare SIVV with traditional pulsed-wave Doppler measurements.Design: Prospective, comparative study.Setting: Animal research laboratory at a university medical center.Subjects: Eight piglets weighing 10-15 kg.Interventions: Hemodynamic instability was induced by using inhalation of isoflurane and infusions of colloid and dobutamine.Measurements: SIVV CO was measured at the left ventricular outflow tract, the aortic valve, and ascending aorta. Transit time CO was used as the reference standard.Results: There was good agreement between SIVV and transit time CO. At high frame rates, the mean difference ± 2 sd between the two methods was 0.01 ± 0.27 L/min for measurements at the left ventricular outflow tract, 0.08 ± 0.26 L/min for the ascending aorta, and 0.06 ± 0.25 L/min for the aortic valve. At low frame rates, measurements were 0.06 ± 0.25, 0.19 ± 0.32, and 0.14 ± 0.30 L/min for the left ventricular outflow tract, ascending aorta, and aortic valve, respectively. There were no differences between the three sites at high frame rates. Agreement between pulsed-wave Doppler and transit time CO was poorer, with a mean difference ± 2 sd of 0.09 ± 0.93 L/min. Repeated SIVV measurements taken at a period of relative hemodynamic stability differed by a mean difference ±2 sd of 0.01 ± 0.22 L/min, with a coefficient of variation = 7.6%. Intraobserver coefficients of variation were 5.7%, 4.9%, and 4.1% at the left ventricular outflow tract, ascending aorta, and aortic valve, respectively. Interobserver variability was also small, with a coefficient of variation = 8.5%.Conclusions: SIVV is an accurate and reproducible flow measurement technique. It is a considerable improvement over currently used methods and is applicable to pediatric critical care.
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| 8. |
- Seoane, Fernando, 1976-, et al.
(författare)
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Brain electrical impedance at various frequencies : the effect of hypoxia
- 2004
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Ingår i: Proceedings of the 26th Annual International Conference of the IEEE EMBS, San Francisco, CA, USA • September 1-5, 2004. - : IEEE Engineering in Medicine and Biology Society. - 0780384393 ; 3, s. 2322-5
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Konferensbidrag (refereegranskat)abstract
- Non-invasive multi-frequency measurements of transcephalic impedance, both reactance and resistance, can efficiently detect cell swelling of brain tissue and can be used for early detection of threatening brain damage. We have performed experiments on piglets to monitor transcephalic impedance during hypoxia. The obtained results have confirmed the hypothesis that changes in the size of cells modify the tissue impedance. During tissue inflammation after induced hypoxia, cerebral tissue exhibits changes in both reactance and resistance. Those changes are remarkably high, up to 71% over the baseline, and easy to measure especially at certain frequencies. A better understanding of the electrical behaviour of cerebral tissue during cell swelling would lead us to develop effective non-invasive clinical tools and methods for early diagnosis of cerebral edema and brain damage prevention.
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| 9. |
- Murphy, M J, et al.
(författare)
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Adaptive filtering to predict lung tumor motion during free breathing
- 2002
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Ingår i: CARS 2002. - BERLIN : SPRINGER-VERLAG BERLIN. - 3540436553 ; , s. 539-544
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Konferensbidrag (refereegranskat)abstract
- Breathing-induced tumor motion during radiation therapy can be compensated either by crating or correcting the pointing of the radiation beam, but these techniques involve time delays in the corrective response. We have analyzed the accuracy of adaptive filter algorithms in predicting tumor positions with sufficient lead time to compensate for these systematic delays. Tumor and chest motion during respiration has been recorded fluoroscopically for lung cancer patients, using gold fiducials implanted in the tumors to enhance visibility. The motions been analyzed for predictability up to 1.0 second in advance Using tapped delay line, Kalman filter, and neural network filter algorithms. Breathing patterns are not stationary in time. Both internal tumor and external chest movement can show amplitude and period modulations during a 30 second interval. Tapped delay line and other stationary filters cannot compensate for the changes and consequently have poor predictability. The predictive accuracy of adaptive filters has little dependence oil the type of algorithm, but depends mainly on the frequency of updating and deteriorates rapidly when predicting more than 0.2 seconds in advance of the breathing signal. Longer-period (e.g., 30 seconds) variability in breathing requires frequent adaptation of the filter parameters.
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