Biofluid optics (BFO) team
The biofluid optics (BFO) team is one research group at the Department of Biomedical Engineering, Technomedicum, Tallinn University of Technology. The main research field of the BFO team is to develop novel optical methods to estimate dialysis adequacy and quality securing end stage renal disease (ESRD) patients’ care quality.
Approximately 2.2 million end stage renal disease (ESRD) patients are treated worldwide, 1.5 of them are haemodialysis (HD) patients and the growth of new patients is approximately 7% a year (FreseniusMedicalCareAG 2007). Without the treatment the patients would die rather quickly (after ca 3-4 days) due to complications caused by excessive body water and uremic toxins in the body. A large part of patients’ life quality decrease and HD expenditures are related to hospitalisations and interventions due to the side effects causing high morbidity and mortality (Rayner et al 2004). Therefore, to improve well-being of the patients and cost effectiveness, the society is interested that adequate renal replacement therapy with high quality and minimum complications is offered.
Uremic syndrome is attributed to the progressive retention of a large number of compounds, which under normal conditions are excreted by healthy kidneys. These compounds are called uremic retention solutes, or uremic toxins, when they interact negatively with biological functions. Several organs and organ systems are affected: cardio-vascular, peripheral and central nervous, haematology etc (Vanholder et al 2008).
The retained organic compounds may be divided into 3 groups: (i) small water soluble solutes with a molecule weight MW < 500 Da (e.g. urea, creatinine, uric acid); (ii) middle molecules MW > 500 Da (e.g. β2-microglobulin, cytokines (Interleukin 6)); and (iii) protein- bound solutes (e.g. homocysteine, P-cresol, AGE products, hippuric acid, indoxyl sulfate).
The disadvantages of the existing methods for uremic toxins determination are utilization of disposables or chemicals, rather complicated and expensive measurement procedure. To overcome those difficulties, a monitoring system would be preferable. Recently a good correlation between ultraviolet (UV)-absorbance and several small removed waste solutes (urea, Cr, UA) has been found, indicating that UV-absorbance may enable monitoring of several uremic toxins linked to the malnutrition–inflammation complex syndrome and the risk factors of CVD. The obtained results demonstrate the possibility to follow a single hemodialysis session continuously and to monitor deviations in the dialysator performance by using UV-absorbance. The UV-method does not need blood samples, any disposables or chemicals, is fast, and allows continuous measurements of the standard dialysis adequacy parameters (e.g. Kt/V, URR).
The first integrated dialysis dose monitor in the world, utilising the UV-technology, is the Adimea system (Option Adimea, BBraun Avitum AG) (B. Braun Avitum AG 2010). The heart of the Adimea system is the optical sensor DiaSens, integrated into the HD machine, delivering values of real-time Kt/V or URR for the dialysis team during a treatment
Currently, the research is focused on developing novel optical technologies for:
1) small molecular weight uremic toxins monitoring;
2) middle- and protein bound molecular weight uremic toxins monitoring;
BFO team involves the following members (click on the name to see the publication list of the corresponding author):
I. Fridolin (leader), J. Arund, J. Jerotskaja, D. Karai, R. Kattai, K. Lauri, M. Luman, R. Tanner, R. Tomson, F. Uhlin.
• K. Lauri, R. Tanner, J. Jerotskaja, M. Luman, I. Fridolin (2010), „A HPLC Study of Uremic Fluids Related to Optical Dialysis Adequacy Monitoring“, Int J Art Org, 33(2): pp. 96-104.
• Jerotskaja J, Uhlin F, Fridolin I, Lauri K, Luman M, Fernström A (2010) “Optical on-line monitoring of uric acid removal during dialysis”, Blood Purification, 29:69-74 (on-line DOI: 10.1159/000264269) (http://www.ncbi.nlm.nih.gov/pubmed/19955732)
• Merike Luman, Jana Jerotskaja, Kai Lauri, Ivo Fridolin. (2009) “Dialysis dose and nutrition assessment by optical on-line dialysis adequacy monitor”, Clinical Nephrology, vol 72 (4), pp.303-311. (http://www.ncbi.nlm.nih.gov/pubmed/19825337)
• Kai Lauri, Jürgen Arund, Risto Tanner, Jana Jerotskaja, Merike Luman, Ivo Fridolin (2010). “Behaviour of uremic toxins and UV absorbance in respect to low and high flux dialyzers”, Estonian Journal of Engineering, March 16(1): pp. 95–106 (doi: 10.3176/eng.2010.1.09)
Brain bioelectrical signals
The research is targeted to estimation of the effect of internal (mental disorders) and external (electromagnetic radiation) factors on the brain bioelectric activity, electroencephalographyc (EEG) signal and cognitive processes (event related potential – ERP) and to development of new signal analysis methods for this purpose.
The main aims are:
- development of signal processing methods sensitive for detecting alterations in brain bioelectric signals hidden in their natural variability;
- finding EEG features characteristic for various mental and neural disorders;
- finding relationships between brain electrical oscillations (EEG and ERP), visual cognition and external electromagnetic radiation.
EEG analysis provides promising results to diagnose several nervous diseases which produce alterations in the EEG waveforms (epilepsy) and has been proven being useful for evaluation of the depth of anaesthesia. However, the majority of the EEG signals are close to normal in mental and neurodegenerative disorders (depression, stress, anxiety, Alzheimer, Parkinson disease). Alterations in EEG related to the low-level electromagnetic radiation effects are small. Abnormalities in waveforms are generally mild, hidden in natural variability of the signal and therefore very difficult to detect. New methods are developed by our team: spectral asymmetry index (SASI) (US8244341B2) for distinguishing depression and integration of differences for detecting the effect electromagnetic radiation.
Fast rhythm of modern life and everyday stress raised significantly the role of mental disorders in our society. A total of 260 million European citizens experience some form of brain related neurodegenerative disorders or mental disorders. According to WHO report, depressive disorder is a leading cause of burden of disease nowadays and it is projected to take the first place in the world in 2030. The diagnosis for mental disorders is based on evaluation of the intensity of subjective symptoms by psychiatrists. Therefore, there is a great need for methods for determining depression based on objective symptoms before the subjective symptoms appear. There is a need for objective monitoring of possible appearance of depressive conditions or other mental disorders of high-risk or high-stress workers such as military personnel, police, and rescue workers. Developed in our department new measure SASI based on EEG spectral asymmetry in a single-channel EEG is proved being effective for differentiating between healthy and depressive persons providing discrimination accuracy comparable to that of nonlinear EEG analysis methods. Inexpensive and patient-friendly method is promising for screening of population.
- Hinrikus H, Bachmann M, Suhhova A, Aadamsoo K, Võhma U, Lass J, Tuulik V. 2009. Electroencephalographic spectral asymmetry index for detection of depression. Med Biol Eng Comput, 47:1291-1299.
- Bachmann M, Lass J, Suhhova A, Hinrikus H. 2013. Spectral Asymmetry and Higuchi’s Fractal Dimension Measures of Depression Electroencephalogram. Comput Math Methods Med. 2013:251638.
Increased use of electronic and telecommunication equipment, especially mobile phones, has raised the problem of possible effects of the radio-frequency electromagnetic field (EMF) on human brain physiology and cognition. Reports on possible non-thermal EMF effects have been contradictory and mechanisms behind the effects unclear during decades. Our team proposed and proved experimentally the parametric excitation mechanism of modulated microwave effect on brain bioelectric oscillations based on EMF influence on hydrogen bonding and diffusion. We detected alterations in EEG at the radiation level much lower recommended health protection limits.
Hinrikus H, Bachmann M, Lass J. 2011. Parametric mechanism of excitation of the electroencephalographic rhythms by modulated microwave radiation. International Journal of Radiation Biology, 87:1077-1085.