| 1. |
- deWeert, Michael J., et al.
(författare)
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Analysis of spatial variability in hyperspectral imagery of the uterine cervix in vivo
- 2003
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Ingår i: Proceedings of SPIE. - : SPIE. ; 4959, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- The use of fluorescence and reflectance spectroscopy in the analysis of cervical histopathology is a growing field of research. The majority of this research is performed with point-like probes. Typically, clinicians select probe sites visually, collecting a handful of spectral samples. An exception to this methodology is the Hyperspectral Diagnostic Imaging (HSDI®) instrument developed by Science and Technology International. This non-invasive device collects contiguous hyperspectral images across the entire cervical portio. The high spatial and spectral resolution of the HSDI instruments make them uniquely well suited for addressing the issues of coupled spatial and spectral variability of tissues in vivo. Analysis of HSDI data indicates that tissue spectra vary from point to point, even within histopathologically homogeneous regions. This spectral variability exhibits both random and patterned components, implying that point monitoring may be susceptible to significant sources of noise and clutter inherent in the tissue. We have analyzed HSDI images from clinical CIN (cervical intraepithelial neoplasia) patients to quantify the spatial variability of fluorescence and reflectance spectra. This analysis shows the spatial structure of images to be fractal in nature, in both intensity and spectrum. These fractal tissue textures will limit the performance of any point-monitoring technology.
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| 2. |
- Ekman, Stefan, et al.
(författare)
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Skånes lavar
- 2003
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Ingår i: Floran i Skåne. Vegetation och utflyktsmål.. - 9197102148 ; , s. 125-132
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Bokkapitel (populärvet., debatt m.m.)
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| 3. |
- Eriksson, Ulf G, et al.
(författare)
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Pharmacokinetics of melagatran and the effect on ex vivo coagulation time in orthopaedic surgery patients receiving subcutaneous melagatran and oral ximelagatran : a population model analysis
- 2003
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Ingår i: Clinical Pharmacokinetics. - 0312-5963 .- 1179-1926. ; 42:7, s. 687-701
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Forskningsöversikt (refereegranskat)abstract
- OBJECTIVE: Ximelagatran, an oral direct thrombin inhibitor, is rapidly bioconverted to melagatran, its active form. The objective of this population analysis was to characterise the pharmacokinetics of melagatran and its effect on activated partial thromboplastin time (APTT), an ex vivo measure of coagulation time, in orthopaedic surgery patients sequentially receiving subcutaneous melagatran and oral ximelagatran as prophylaxis for venous thromboembolism. To support the design of a pivotal dose-finding study, the impact of individualised dosage based on bodyweight and calculated creatinine clearance was examined. DESIGN AND METHODS: Pooled data obtained in three small dose-guiding studies were analysed. The patients received twice-daily administration, with either subcutaneous melagatran alone or a sequential regimen of subcutaneous melagatran followed by oral ximelagatran, for 8-11 days starting just before initiation of surgery. Nonlinear mixed-effects modelling was used to evaluate rich data of melagatran pharmacokinetics (3326 observations) and the pharmacodynamic effect on APTT (2319 observations) in samples from 216 patients collected in the three dose-guiding trials. The pharmacokinetic and pharmacodynamic models were validated using sparse data collected in a subgroup of 319 patients enrolled in the pivotal dose-finding trial. The impact of individualised dosage on pharmacokinetic and pharmacodynamic variability was evaluated by simulations of the pharmacokinetic-pharmacodynamic model. RESULTS: The pharmacokinetics of melagatran were well described by a one-compartment model with first-order absorption after both subcutaneous melagatran and oral ximelagatran. Melagatran clearance was correlated with renal function, assessed as calculated creatinine clearance. The median population clearance (creatinine clearance 70 mL/min) was 5.3 and 22.9 L/h for the subcutaneous and oral formulations, respectively. The bioavailability of melagatran after oral ximelagatran relative to subcutaneous melagatran was 23%. The volume of distribution was influenced by bodyweight. For a patient with a bodyweight of 75kg, the median population estimates were 15.5 and 159L for the subcutaneous and oral formulations, respectively. The relationship between APTT and melagatran plasma concentration was well described by a power function, with a steeper slope during and early after surgery but no influence by any covariates. Simulations demonstrated that individualised dosage based on creatinine clearance or bodyweight had no clinically relevant impact on the variability in melagatran pharmacokinetics or on the effect on APTT. CONCLUSIONS: The relatively low impact of individualised dosage on the pharmacokinetic and pharmacodynamic variability of melagatran supported the use of a fixed-dose regimen in the studied population of orthopaedic surgery patients, including those with mild to moderate renal impairment.
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| 4. |
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| 5. |
- Gustafsson, Agnetha, et al.
(författare)
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Evaluation of various attenuation corrections in lung SPECT in healthy subjects
- 2003
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Ingår i: Nuclear Medicine Communications. - : Ovid Technologies (Wolters Kluwer Health). - 0143-3636 .- 1473-5628. ; 24:10, s. 1087-1095
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Tidskriftsartikel (refereegranskat)abstract
- The effect of increasingly more sophisticated attenuation correction methods on image homogeneity has been studied in seven healthy subjects. The subjects underwent computed tomography (CT), single photon emission computed tomography (SPECT) and transmission computed tomography (TCT) of the thorax region in the supine position. Density maps were obtained from the CT and TCT studies. Attenuation corrections were performed using five different methods: (1) uniform correction using only the body contour; (2) TCT based corrections using the average lung density; (3) TCT based corrections using the pixel density; (4) CT based corrections using average lung density; and (5) CT based corrections using the pixel density. The isolated attenuation effects were assessed on quotient images generated by the division of images obtained using various attenuation correction methods divided by the non-uniform attenuation correction based on CT pixel density (reference method). The homogeneity was calculated as the coefficient of variation of the quotient images (CVatt), showing the isolated attenuation effects. Values of CVatt were on average 12.8% without attenuation correction, 10.7% with the uniform correction, 8.1% using TCT map using the average lung density value and 4.8% using CT and average lung density corrections. There are considerable inhomogeneities in lung SPECT slices due to the attenuation effect. After attenuation correction the remaining inhomogeneity is considerable and cannot be explained by statistical noise and camera non-uniformity alone. ((C) 2003 Lippincott Williams Wilkins).
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| 6. |
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| 7. |
- Gustafsson, Harald, et al.
(författare)
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Dual-Microphone Spectral Subtraction
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Mobile phones are constantly decreasing in size, thereby complicating the acoustical functionality. Signal processing methods can be used to partially mitigate this problem. In this paper we suggest a method which uses multiple spectral subtraction functions and two microphones, introducing only a short signal delay. The idea is to use spectral subtraction methods to extract the noise as well as the speech during a single time-frame. The environment background noise may not be stationary, thereby limiting the method to only employ short estimates of the background noise signal. Results are presented for experiments in various environments, showing a reduced noise level in the processed signal compared with the un-processed signal, and with preserved speech quality.
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| 8. |
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| 9. |
- Gustafsson, Oscar, 1973-
(författare)
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On mapping of digital filter algorithms to hardware
- 2000
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis we discuss various issues involving the design path for low power design of frequency-selective digital filters. As recursive filters have a bound on the minimal iteration period, Tmin we focus on these. Implementations that obtain Tmin are known as maximally fast.The main idea to obtain a low power implementation is to use a maximally fast implementation and trade any excess speed for lower power consumption by decreasing the power supply voltage.We show that using three-port adaptor allpass sections and constrained third-order allpass sections for implementation of maximally fast lattice wave digital filters are advantageous compared with second-order Richards' structures.We further show that maximally fast ladder wave digital filters can be efficiently implemented using the same techniques as for lattice wave digital filters, despite that they have a more complex structure with many loops.We also show that maximally fast digital filters can be implemented using a numerically equivalent state-space representation and distributed arithmetic. As the latency of distributed arithmetic is dependent on the number of fractional bits of the longest coefficient, it may decrease the performance if the critical loop is through one of the shorter coefficients. However, we show that by modifying the contents of the ROM we can achieve Tmin independent of the other coefficients in the ROM.Further, we introduce single filter frequency masking. In this approach we substitute the different subfilters in narrow-band frequency masking and frequency-response masking structures to identical subfilters (except for the periodicity). By mapping the subfilters to the same hardware structure using folding an efficient hardware implementation is obtained. This approach is discussed for narrow-band lowpass recursive and FIR filters, and for frequency-response masking structures based on FIR filters.
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| 10. |
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