Joanna Bauer

Electrically Polarized Biomaterials.

Electrically polarized biomaterials and their interactions with the surrounding biological environment is important for understanding the host response, growth and inhibition of biological species as well as the long-term fate and performance of the implants. Polarized materials possess electrical charges at the surface due to polar or electret properties. As these surfaces are at the frontier of biological reactions understanding biological interactions at the interface with polarized biomaterials requires a convergence of understanding multiple disciplines. This article discusses progress that has taken place in the fields of surface and interface science, materials science and biomedical device engineering to obtain a better perspective of such interactions.

Electrical properties of hydroxyapatite

Abstract Despite being one of the mostly studied biomaterials for orthopedic, dental, protein purification and stem cell applications, electrical properties of hydroxyapatite has received only limited attention. Since the prediction in 2005 of the possibility of piezo and pyroelectricity in hydroxyapatite several theoretical and experimental works in this field may lead to new understandings of electrical behaviors of calcified tissues in vertebrates. Also, the ability of creating discrete electrostatic domains on nanocrystalline films of hydroxyapatite will open the possibility of understanding how surface charge influences biological interactions. The outlook for future endeavours in this field will be discussed.

Neural network and optical correlators for infrared imaging based face recognition

This paper deals with the problem of thermovision application for biometric people recognition. The main goal of research was the automatization of recognition process and proving, whether the infrared imaging can be exploited for realization of the biometric system. First, the data base composed of 270 images made in different conditions, was built. Next, the multilayer perception and two optical correlators such as joint transform correlator and 4f correlator, were applied. Each system was designed for realizing two various tasks: verification and identification. Finally, the systems were tested and evaluated according to the Face Recognition Vendor Tests (FRVT). Achieved results proved that temperature distribution on the human face is a biometric trait and people can be efficiently recognized with usage of infrared imagery.

Pattern recognition of transillumination images for diagnosis of rheumatoid arthritis

In this work the statistical pattern recognition methods were applied for evaluation of transillumination images of interphalangeal joints of patients suffering from rheumatoid arthritis. Special portable apparatus was constructed for performing the transillumination examination. It consisted of He-Ne laser with optics for collimated illumination, special holder for placing the finger (perpendicular to optical axis, dorsal site towards camera), and CCD camera with memory stick. 20 ill patients and 20 healthy volunteers were examined. The captured images with 1152x864 resolution were converted into the gray level pictures and analyzed by means of statistical pattern recognition method. Principal Component Analysis (PCA) and cluster analysis by use of 1-NN method (1 Nearest Neighbour) were applied for classification. The recognition system was able to differentiate correctly between healthy and ill subjects with 72.35% accuracy in case the data base composed of 40 persons.

Electrically Active Materials for Medical Devices

Electrical properties of hydroxyapatite (HA) in the form of screen printed thick films that can be used as a biocompatible coating for bone and dental implants are reported. In particular, piezo- and pyroelectric behaviour of these films suggest that they can be used to promote faster healing of bones and prevent rejection of implants. Moreover, the reversible pressure-induced changes in their electrical characteristics can be employed for real-time in vivo pressure sensors implantable simultaneously, for example, with knee or hip prosthesis. The additional advantage of HA in the form of screen-printed thick films is that, due to the technology’s versatility, it can be produced on flexible substrate in any shape and size to suit the needs of various patients.

Laser transillumination for diagnosis of rheumatoid arthritis

In this work, the special portable apparatus was constructed for performing the transillumination examination on interphalangeal joints of patients suffering from rheumatoid arthritis. It consisted of He-Ne laser with optics for collimated illumination, special holder for placing the finger (perpendicular to optical axis, dorsal site towards camera), and CCD camera with memory stick. The captured images in JPEG format with 1152x864 resolution were converted into the gray level pictures and analyzed by means of image processing program from OPTIMAS. 35 ill patients and 11 healthy volunteers were examined. The histograms and 35 luminances were calculated. The average function was applied in order to calculate the mean gray level values in images of corresponding fingers of healthy subjects. These values were compared with values calculated for ill persons. We proved that that transillumination images may have a diagnostic value. For RA suffering patients the corresponding transillumination images represented the lower gray level values than the average value of finger of health volunteers. For II finger of left hand 96% images of ill persons have lower gray level and in case of right hand it was 93%. This proves that basing in transillumination one can diagnose with high probability the patient with rheumatoid arthritis.

Performance repeatability of fiberoptics applicators for laser therapy

The distribution of light emitted from the sol-gel coated fiberoptic applicator for interstitial laser therapy was examined. The silica sol-gel coatings were prepared from silicate precursor TEOS (tetraethylorthosilicate) mixed with ethyl alcohol in acid catalyzed hydrolysis. The applicator was produced with ratio R = 20, whereas R denotes the number of solvent moles (ethanol) to the number of TEOS moles. Then, the light pattern was captured by means of CCD camera and statistical pattern recognition method was applied to study the repeatability of light distribution. Two methods were applied: Fisher Linear Discriminant Analysis (FLDA) and Principal Component Analysis (PCA). The top match characteristic TM as calculated by statistical pattern recognition methods was taken as a factor corresponding to the performance repeatability. It was demonstrated that is possible to produce the sol-gel applicators with more than 92% repeatability.

Optical correlators for recognition of human face thermal images

In this paper, the application of the optical correlators for face thermograms recognition is described. The thermograms were colleted from 27 individuals. For each person 10 pictures in different conditions were recorded and the data base composed of 270 images was prepared. Two biometric systems based on joint transform correlator and 4f correlator were built. Each system was designed for realizing two various tasks: verification and identification. The recognition systems were tested and evaluated according to the Face Recognition Vendor Tests (FRVT).

Human body as a set of biometric features identified by means of optoelectronics

Human body posses many unique, singular features that are impossible to copy or forge. Nowadays, to establish and to ensure the public security requires specially designed devices and systems. Biometrics is a field of science and technology, exploiting human body characteristics for people recognition. It identifies the most characteristic and unique ones in order to design and construct systems capable to recognize people. In this paper some overview is given, presenting the achievements in biometrics. The verification and identification process is explained, along with the way of evaluation of biometric recognition systems. The most frequently human biometrics used in practice are shortly presented, including fingerprints, facial imaging (including thermal characteristic), hand geometry and iris patterns.

Biometric verification of persons based on thermovision

Biometrics is recently a key interest of many institutions, especially those interested in public security. Biometrics relies on recognition, identification and verification of physiological or/and behavioral features of human body. These include e.g. fingerprints, retina or iris images, examination of DNA or way of handwriting and many others. Face recognition is one of these modalities. The successful security systems should offer high efficiency, meaning high rate of properly classified and verified images. They should be also free from external disturbances like unstable environment conditions, illumination etc. In this paper we demonstrated that biometric verification based on the analysis of thermal images could fulfill these requirements and thermal image of the human face can be regarded as a biometric feature, as well. Analyzed database incorporates thermal images of 26 adults, registered by high quality infrared camera AGEMA 900 LW in various conditions under the influence of externally induced changes to the thermal characteristics. In order to perform the image processing the compression step was applied, so the acquired 270 x 135 pixels image was reduced to the size of 85 x 85 pixels. The reduced images were further analyzed. Our system worked in three regimes, based on Eigenfaces, Fisherfaces and joint transform correlator. Receiver Operator Characteristic was used for evaluation of each of the mentioned above modalities. Equal Error Rate was applied for evaluation of the tested systems. It was shown that the highest rate of system efficiency was achieved by implementation of Fisherfaces 96,54% and joint transform correlator 88,40%. Thus, it was also demonstrated that temperature distribution can be regarded as biometrics feature and can be used for person verification.