Lékař a technika - Clinician and Technology

DYNAMIC MECHANICAL PROPERTIES OF NATIVE ENDPLATE

Josef Šepitka — 2023-06-30

A study of mechanical properties of native tissues is a great challenge in biomechanics. Especially, hardly accessible structures that play a very important role within a locomotive system. A study of a cartilaginous endplate (CEP) is just such a challenge. CEP is approximately 0.6 mm thin layer of hyaline cartilage between an intervertebral disc (IVD) and a vertebral body (VB). A calcification or any mechanical damage of CEP can cause restrictions of nutrition and metabolic waste flow inward and outward from IVD, respectively. Degenerative processes influence mechanical properties of the tissue. Due to very small thickness of CEP, instrumental nanoindentation seems to be suitable method for this task. This paper presents a study of time dependent viscoelastic properties of native porcine CEP using nanoscale dynamic mechanical analysis in the range of frequency from 5 Hz to 215 Hz. The storage moduli were obtained in the range from 11.78 MPa to 17.11 MPa. The loss moduli were obtained in the range from 2.96 MPa to 5.32 MPa.

INFRARED THERMOGRAPHY - COMPARISON OF INNER CANTHUS OF THE EYES AND FOREHEAD SURFACE TEMPERATURES IN HEALTHY ADULTS

Vladan Bernard — 2023-06-30

Infrared thermography (IRT) is a non-invasive method for surface temperature measuring. The use of the contactless IRT method is comfortable for the patient, fast and hygienic. However, this method does not provide information about the core body temperature because the temperature is measured indirectly from the surface of the human body. There are several places on a human body from which surface temperature is commonly measured; the methods of measurement and application of the device is inconsistent. The aim of this article is to show the difference between the temperature measured on the forehead and on the inner corner of the eye in healthy persons, with reference to the recommendations of ISO standard. This is mainly due to the fact that compliance with the ISO standard is not always met, as shown by the personal experience of the authors. The body surface temperature was measured by use infrared camera WIC 640 under control of calibrated model of a black body. The data from 59 different volunteer subjects show statistically significant difference in measured temperature from both selected positions. The obtained median temperature values were 35.04 °C from forehead area and 35.85 °C from canthus of eyes. The observed difference was more than three-quarters of a degree Celsius for the median value. The maximum observed temperature difference within the observed group was almost 1.94 °C. The present study defines surface temperature from canthus of eye and undoubtedly shows how important it is to comply with the standards and recommendations of professional thermology societies.

SURFACE BIOCOMPATIBILITY OF POROUS TITANIUM STRUCTURES WITH STEM CELLS

Marianna Trebuňová — 2023-06-30

Successful tissue regeneration requires scaffolds with mechanical stability or biodegradability, surface roughness, and porosity to provide a suitable microenvironment for sufficient cell interaction, migration, cell proliferation, and differentiation. This study features the design, fabrication, and biocompatibility testing of Ti-6Al-4V titanium alloy scaffolds. Cylindrical titanium samples were tested, where each sample had a porous structure with pore sizes of 0.4 mm, 0.8 mm, and 1.0 mm respectively, which were seeded with chorionic-derived mesenchymal stem cells (CMSCs). The viability of the seeded CMSCs was evaluated using the MTT test. The aim of the study was to evaluate the cytotoxic effect and biocompatibility of porous titanium scaffolds. CMSCs showed the highest viability, adhesion to surfaces, and good proliferation on samples with 0.4 mm pore size, on the other hand, the pore size of 1.0 mm showed relatively lowest compatibility with cells and their proliferation. However, the viability of cells on all tested sizes of porous titanium scaffolds showed sufficient viability for future use in regenerative medicine.

NON-INVASIVE PPG-BASED ESTIMATION OF BLOOD GLUCOSE LEVEL

Enikö Vargová — 2023-06-30

This paper focuses on non-invasive blood glucose determination using photoplethysmographic (PPG) signals, which is crucial for managing diabetes. Diabetes stands as one of the world’s major chronic diseases. Untreated diabetes frequently leads to fatalities. Current self-monitoring techniques for measuring diabetes require invasive procedures such as blood or bodily fluid sampling, which may be very uncomfortable. Hence, there is an opportunity for non-invasive blood glucose monitoring through smart devices capable of measuring PPG signals. The primary goal of this research was to propose methods for glycemic classification into two groups (low and high glycemia) and to predict specific glycemia values using machine learning techniques. Two datasets were created by measuring PPG signals from 16 individuals using two different smart devices – a smart wristband and a smartphone. Simultaneously, the reference blood glucose levels were invasively measured using a glucometer. The PPG signals were preprocessed, and 27 different features were extracted. With the use of feature selection, only 10 relevant features were chosen. Numerous machine learning models were developed. Random Forest (RF) and Support Vector Machine (SVM) with the radial basis function (RBF) kernel performed best in classifying PPG signals into two groups. These models achieved an accuracy of 76% (SVM) and 75% (RF) on the smart wristband test dataset. The functionality of the proposed models was then verified on the smartphone test dataset, where both models achieved similar accuracy: 74% (SVM) and 75% (RF). For predicting specific glycemia values, RF performed best. Mean Absolute Error (MAE) was 1.25 mmol/l on the smart wristband test dataset and 1.37 mmol/l on the smartphone test dataset.

DESIGN AND TESTING OF A DEVICE FOR HUMAN LIMB MULTIFREQUENCY COMPARATIVE BIOIMPEDANCE MEASUREMENT– PRELIMINARY STUDY

Martin Schmidt — 2023-06-30

Bioimpedance is the ability of biological tissues to impede the flow of electrical current. It is often measured as a means of detecting volume and structural changes in various biological tissues. The purpose of this work was to design a two-channel portable device for measuring multifrequency bioimpedance of human limbs. The device was constructed specifically for evaluation of the bioimpedance measurement as a possible tool for aiding in diagnosis of soft-tissue structural changes in the muscles of human limbs by continuously comparing bioimpedance of one limb to the other. The proposed device is based on impedance converter AD5933. It is designed for noninvasive measurements on the human body with low amplitude alternating current at frequencies between 1 kHz and 100 kHz. The device was tested for electromagnetic compatibility, accuracy and used in laboratory measurements for detection of muscle edema on a bioimpedance model. It is capable of measuring impedance up to 100 kΩ with a relative measurement error below 1.84%.