| 1. |
|
|
| 2. |
- Jalkanen, Ville, 1978-, et al.
(författare)
-
Explanatory models for a tactile resonance sensor system-elastic and density-related variations of prostate tissue in vitro
- 2008
-
Ingår i: Physiological Measurement. - Bristol : IOP Publ. Ltd. - 0967-3334 .- 1361-6579. ; 29:7, s. 729-745
-
Tidskriftsartikel (refereegranskat)abstract
- Tactile sensors based on piezoelectric resonance have been adopted for medical applications. The sensor consists of an oscillating piezoelectric sensor–circuit system, and a change in resonance frequency is observed when the sensor tip contacts a measured object such as tissue. The frequency change at a constant applied force or mass load is used as a stiffness-sensitive parameter in many applications. Differential relations between force and frequency have also been used for monitoring intraocular pressure and stiffness variations in prostate tissue in vitro. The aim of this study was to relate the frequency change (Δf), measured force (F) and the material properties, density and elasticity to an explanatory model for the resonance sensor measurement principle and thereby to give explanatory models for the stiffness parameters used previously. Simulations of theoretical equations were performed to investigate the relation between frequency change and contact impedance. Measurements with a resonance sensor system on prostate tissue in vitro were used for experimental validation of the theory. Tissue content was quantified with a microscopic-based morphometrical method. Simulation results showed that the frequency change was dependent upon density (ρ) and contact area (S) according to Δf ∝ ρS3/2. The experiments followed the simulated theory at small impression depths. The measured contact force followed a theoretical model with the dependence of the elastic modulus (E) and contact area, F ∝ ES3/2. Measured density variations related to histological variations were statistically weak or non-significant. Elastic variations were statistically significant with contributions from stroma and cancer relative to normal glandular tissue. The theoretical models of frequency change and force were related through the contact area, and a material-dependent explanatory model was found as Δf ∝ ρE−1F. It explains the measurement principle and the previously established stiffness parameters from the material properties point of view.
|
|
| 3. |
- Jalkanen, Ville, 1978-, et al.
(författare)
-
Prostate tissue stiffness as measured with a resonance sensor system : a study on silicone and human prostate tissue in vitro.
- 2006
-
Ingår i: Medical and Biological Engineering and Computing. - : Springer Science and Business Media LLC. - 0140-0118 .- 1741-0444. ; 44:7, s. 593-603
-
Tidskriftsartikel (refereegranskat)abstract
- Prostate cancer is the most common form of cancer in men in Europe and in the USA. Some prostate tumours are stiffer than the surrounding normal tissue, and it could therefore be of interest to measure prostate tissue stiffness. Resonance sensor technology based on piezoelectric resonance detects variations in tissue stiffness due to a change in the resonance frequency. An impression-controlled resonance sensor system was used to detect stiffness in silicone rubber and in human prostate tissue in vitro using two parameters, both combinations of frequency change and force. Variations in silicone rubber stiffness due to the mixing ratio of the two components could be detected (p<0.05) using both parameters. Measurements on prostate tissue showed that there existed a statistically significant (MANOVA test, p<0.001) reproducible difference between tumour tissue (n=13) and normal healthy tissue (n=98) when studying a multivariate parameter set. Both the tumour tissue and normal tissue groups had variations within them, which were assumed to be related to differences in tissue composition. Other sources of error could be uneven surfaces and different levels of dehydration for the prostates. Our results indicated that the resonance sensor could be used to detect stiffness variations in silicone and in human prostate tissue in vitro. This is promising for the development of a future diagnostic tool for prostate cancer.
|
|
| 4. |
- Jalkanen, Ville, 1978-, et al.
(författare)
-
Resonance sensor measurements of stiffness variations in prostate tissue in vitro : a weighted tissue proportion model
- 2006
-
Ingår i: Physiological Measurement. - : IOP Publishing. - 0967-3334 .- 1361-6579. ; 27:12, s. 1373-86
-
Tidskriftsartikel (refereegranskat)abstract
- Prostate cancer is the most common type of cancer in men in Europe and the US. The methods to detect prostate cancer are still precarious and new techniques are needed. A piezoelectric transducer element in a feedback system is set to vibrate with its resonance frequency. When the sensor element contacts an object a change in the resonance frequency is observed, and this feature has been utilized in sensor systems to describe physical properties of different objects. For medical applications it has been used to measure stiffness variations due to various patho-physiological conditions. In this study the sensor's ability to measure the stiffness of prostate tissue, from two excised prostatectomy specimens in vitro, was analysed. The specimens were also subjected to morphometric measurements, and the sensor parameter was compared with the morphology of the tissue with linear regression. In the probe impression interval 0.5-1.7 mm, the maximum R(2) > or = 0.60 (p < 0.05, n = 75). An increase in the proportion of prostate stones (corpora amylacea), stroma, or cancer in relation to healthy glandular tissue increased the measured stiffness. Cancer and stroma had the greatest effect on the measured stiffness. The deeper the sensor was pressed, the greater, i.e., deeper, volume it sensed. Tissue sections deeper in the tissue were assigned a lower mathematical weighting than sections closer to the sensor probe. It is concluded that cancer increases the measured stiffness as compared with healthy glandular tissue, but areas with predominantly stroma or many stones could be more difficult to differ from cancer.
|
|
| 5. |
- Lindberg, Peter L, et al.
(författare)
-
An image analysis method for prostate tissue classification : preliminary validation with resonance sensor data
- 2009
-
Ingår i: Journal of Medical Engineering & Technology. - : Informa healthcare. - 0309-1902 .- 1464-522X. ; 33:1, s. 18-24
-
Tidskriftsartikel (refereegranskat)abstract
- Resonance sensor systems have been shown to be able to distinguish between cancerous and normal prostate tissue, in vitro. The aim of this study was to improve the accuracy of the tissue determination, to simplify the tissue classification process with computerized morphometrical analysis, to decrease the risk of human errors, and to reduce the processing time. In this article we present our newly developed computerized classification method based on image analysis. In relation to earlier resonance sensor studies we increased the number of normal prostate tissue classes into stroma, epithelial tissue, lumen and stones. The linearity between the impression depth and tissue classes was calculated using multiple linear regression (R(2) = 0.68, n = 109, p < 0.001) and partial least squares (R(2) = 0.55, n = 109, p < 0.001). Thus it can be concluded that there existed a linear relationship between the impression depth and the tissue classes. The new image analysis method was easy to handle and decreased the classification time by 80%.
|
|
| 6. |
|
|
| 7. |
- Öberg, Henrik, et al.
(författare)
-
Stability of Pt-Modified Cu(111) in the Presence of Oxygen and Its Implication on the Overall Electronic Structure
- 2013
-
Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:32, s. 16371-16380
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure and stability of Cu(111)-hosted Pt overlayers with and without the presence of atomic oxygen have been studied by means of core-level spectroscopy and density functional theory (DFT). Because of lattice mismatch, Pt(111) overlayers grown on Cu(111) are compressively strained, and hard X-ray photoelectron spectroscopy together with Pt L-3-edge X-ray absorption spectroscopy (XAS) reveals a pronounced downshift of the Pt d-band owing to the increased overlap of the d-orbitals, an effect also reproduced theoretically. Exposure to oxygen severely alters the surface composition; the O-Cu binding energy largely exceeds that of O-Pt, and DFT calculations predict surface segregation of Cu atoms. Comparing the adsorbate electronic structure for O on unstrained Pt(111) with that of O on Pt-modified Cu(111) using O K-edge XAS and X-ray emission spectroscopy salient differences are observed and calculations show that Cu-segregation to the topmost layer is required to reproduce the measured spectra. It is proposed that O is binding in a hollow site constituted by at least two Cu atoms and that up to 75% of the Pt atoms migrate below the surface.
|
|
| 8. |
- Eneman, Marie, 1969, et al.
(författare)
-
Regulating Police Body-Worn Camera Practice - A Four Modality Perspective
- 2019
-
Ingår i: Proceedings of the 10th Scandinavian Conference on Information Systems (SCIS), Finland, 2019. - : Association for Information Systems.
-
Konferensbidrag (refereegranskat)abstract
- Police authorities in a number of countries have recently introduced body-worn cameras (BWC). With the use of body-worn cameras, the police have gained access to new forms of wearable and powerful law enforcing technologies. The cameras enable collection of large volume of personal information and in some cases even sensitive information that must be managed and stored within the organisation in line with rules of law. As is often the case when technology develops faster than societal norms and values, a range of questions concerning issues related to regulation of these practises are still uninvestigated. Therefore, this paper will analyse what actually regulates individual police officers’ body-worn camera practice. Empirically, we use the Swedish police as a case and our study is based on qualitative interviews. Theoretically we draw upon Lawrence Les-sig’s four modality model - law, norms, market, and architecture - and we conclude that i) law is considered important although law regarding BWC is still in its infancy, ii) while law and official directives have a more macro applicability, norms are developed and maintained more locally, iii) market regulate indirectly via availability and cost, and iv) architecture is not necessarily as self-executed as often stated.
|
|
| 9. |
- Gustafsson, Agnetha, et al.
(författare)
-
Evaluation of attenuation corrections using Monte Carlo simulated lung SPECT
- 1998
-
Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 43:8, s. 2325-2336
-
Tidskriftsartikel (refereegranskat)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
|
|
| 10. |
|
|
