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Biomedical subjects

M Juhola

Publications and source records attributed to M Juhola.

At least 109 records · Page 6Linked to original sources
PubMed1994

Parameters for a knowledge base for acute appendicitis.

Acute appendicitis is the most common cause of acute abdomen requiring surgical intervention. The clinical diagnosis of acute appendicitis is not always easy due to variable symptomatology, particularly at the onset. The contributions of history-taking and physical examination in the diagnosis of acute appendicitis was studied in connection with the Research Committee of the World Organization of Gastroenterology (OMGE) survey of acute abdominal pain. Especially the suitability of diagnostic parameters in the construction of an expert system for automatic decision making was studied. The results clearly show that it is possible to construct an expert system for automatic decision making in the diagnosis of acute appendicitis.

Abdomen, Acute↗
PubMed1993

On digital filtering of auditory brainstem responses.

Auditory brainstem responses are very short events. Therefore, their signal processing has to be executed really carefully. Their latency and amplitude parameters, which are employed to indicate pathological changes, are especially sensitive to digital filtering. Consequently, we have studied appropriate nonrecursive and recursive filters for signals of auditory brainstem responses. Our results seem to refer to rather similar effects of both nonrecursive and recursive filters on the parameters of auditory brainstem responses.

Adult↗
PubMed1993

A measurement system of head movements for the vestibulo-ocular reflex.

This paper describes an efficient technique to record head movement signals for the computer analysis of vestibulo-ocular reflex. The technique has essentially lower costs than the method of rotatory chair. It is easy to operate and yields recordings of high quality. The system is connected to our analysis program of vestibulo-ocular reflex, the results of which are briefly presented.

Costs and Cost Analysis↗
PubMed1992

Evaluation of some nonrecursive digital filters for signals of auditory evoked responses.

Auditory brain stem evoked responses are routinely used in audiology and otoneurology. Because recordings include more or less noise, the signals of evoked responses need digital filtering to suppress the noise. Nonrecursive digital filters are often the best since they can be organized to have no phase shift, which is essential in order not to distort sensitive parameters, as latency, in evoked responses. We have studied effects of some nonrecursive digital filters on the latency parameters of evoked responses. It turned out that digital filtering can have considerable influence on latencies, and thus the choice of appropriate filters is crucial.

Evaluation Studies as Topic↗
PubMed1992

On identification of saccades from sinusoidal eye movement signals.

Sinusoidal eye movements and potential saccadic eye movements are examined using the syntactic pattern recognition method presented previously. A few computer tests are presented for the verification of potential saccades from signals of sinusoidal eye movements. The technique was developed and tested with electro-oculographic signals. The verification of saccades consists of three tests: the estimation of average noise peaks in an eye movement signal; an angular velocity threshold; and the comparison between a sinusoidal eye movement signal and the corresponding stimulus signal. The technique is also efficient for noisy signals of eye movements, which were stimulated by both predictive and non-predictive sinusoidal stimulus movements.

Calibration↗
PubMed1991

A syntactic analysis method for sinusoidal tracking eye movements.

A syntactic method for the recognition of sinusoidal eye movements is presented. The method is based on a piecewise transformation of an eye movement signal to strings of a formal language and use of a formal grammar which generates the formal language. Gain and phase parameters of sinusoidal eye movements between a stimulus and its response are computed after the recognition of eye movements and after removing corrective saccades from the transformed signal. The method is used at an otoneurological laboratory.

Diagnosis, Computer-Assisted↗
PubMed1991

Median filtering is appropriate to signals of saccadic eye movements.

In this paper we show nonlinear standard and hybrid median filters are appropriate to the filtering of signals of saccadic eye movements. Although these filters effectively attenuate noise, they do not harm the parameters of saccades, particularly the maximum velocity which is an important indicator of certain diseases and disorders in man. The filters have been tested by simulation as well as actual eye movement signals recorded electro-oculographically and photoelectrically.

Algorithms↗
PubMed1991

Postural control in blinds and in Usher's syndrome.

The postural control mechanisms were evaluated in 10 blinds and in 10 subjects with Usher's syndrome. The results were compared with 27 age matched healthy volunteers. In visual conditions the subjects with Usher's syndrome performed worse, but in nonvisual condition they performed equally well as the controls. The results were the same irrespective of whether the tests were performed on a rigid surface or foam rubber covered surface. The blinds and controls performed equally well on the bare surface, but the blinds performed significantly better on the foam rubber covered surface. The results indicate that in subjects with Usher's syndrome the vestibulo-cochlear degeneration is well compensated but the postural stability aggravated due to retinal degeneration. Blind subjects have a better postural control than their seeing referents, but the difference is only evident in situations in which the postural control is hampered by surface perturbation.

Adolescent↗
PubMed1991

Effects of digital low pass filtering on the parameters of nystagmus eye movements.

We examined how lowpass filtering has an influence on nystagmus parameters: durations, amplitudes, and mean velocities of its slow and fast phases. We experimented with two types of common linear digital filters by using both nonrecursive and recursive filters, and with two types of nonlinear digital filters by using so-called standard median and hybrid median filters. We concluded that 70 Hz as strict cutoff frequency is high enough not to cause errors in the nystagmus parameters when information content in nystagmus signals is filtered above that cutoff frequency with linear filters. Using nonlinear filters good window lengths of filtering are equal to or less than about nine samples for a sampling frequency of 400 Hz which we applied.

Analog-Digital Conversion↗
PubMed1991

A microcomputer system for assessment of peripheral blood flow. An example of nasal blood flow.

We have designed and implemented a microcomputer system for studying the effect of various mediator substances on the nasal blood flow. The system uses an IBM PC/AT microcomputer, which is connected with a Laser Doppler Flowmeter (LDF) and an iontophoretic drug application system. The LDF measures flux from the tissue that in the example is the inferior nasal turbinate. The flux is converted to digital form by an analog-digital converter of 12 bits. The program is implemented in the Pascal language. In the analysis, a flux level, amplitude, rise time and decay time of the pulse wave are determined. The effect of drugs on the flux can be studied by applying them iontophoretically. In the program the length and number of the drug application periods as well as the recording period are user-driven. In the nasal blood flow iontophoretically administered adrenaline reduced significantly the flux parameters and histamine canceled this effect. Tachyphylalaxis was a frequent observation in repeated measurements. The system can be used to evaluate the role of different transmitters in the etiology of chronic rhinitis.

Adult↗
PubMed1989

A microcomputer system for clinical signal analysis of vestibular laboratory.

A vestibular laboratory system was implemented for clinical testing and medical examination of patients with balance disorders. Programs for analysis of postural control and eye movements were made for a microcomputer. The microcomputer system can be used by a nurse without technical education. The system has now been used for two years at the laboratory.

Eye Movements↗
PubMed1989

Vestibulo-ocular and vestibulo-spinal reflexes in evaluation of vestibular lesions.

In order to evaluate to what extent different diseases causing vertigo can be detected by studying vestibulo-spinal and vestibulo-ocular reflexes, 146 patients were examined. The diagnosis classes were: periodical attacks, position induced attacks, vestibular neuronitis, brain concussion, cerebrovascular disorders and acoustic neurinoma. Dynamic posturography was performed on all the patients, standard bithermal caloric test on 129 and voluntary saccades on 127 patients. The proportion of pathological test results in posturography exceeded that in the caloric test in all but one diagnosis class. In vestibular neuronitis the amount of abnormal test results was low in posturography, probably due to vestibular compensation. Posturography tested with eyes open and with 80 Hz vibration revealed disturbances in equilibrium the most sensitively.

Caloric Tests↗