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T Katila

Publications and source records attributed to T Katila.

At least 37 records · Page 2Linked to original sources
PubMed2001

WWW--an effective way of teaching radiology.

The Internet and especially the World Wide Web (WWW) have given new opportunities and challenges in teaching radiology. In Kuopio University and Kuopio University Hospital, we started to develop a new WWW-based radiology teaching file in 1996. Our file was made as a result of weaknesses in other files and as an answer to our local needs. The file consists of 1245 separate radiographs in 14 different categories. The language is Finnish, because the target use primarily is basic medical education in Finland. A small part has been translated into English. The quality of images was improved using a separate viewer (Osiris, Digital Imaging Unit, University Hospital of Geneva, Switzerland), which also allowed image manipulation needed with radiological images. We have monitored the utilisation of pages (Analog 1.92 beta-3.0/UNIX) and found the results encouraging. The follow-up time was 814 days (10 February 1997-27 September 1999), the total number of requests was 762797 and that for HTML pages is 288664. Monthly means are 27243 and 10309, respectively. The total number for visited domains is 61. The URL for these pages is http://www.uku.fi/laitokset/klrad/opetuskuvasto/.

Humans↗
PubMed2001

Magnetocardiographic intra-QRS fragmentation analysis in the identification of patients with sustained ventricular tachycardia after myocardial infarction.

The aim of this study was to investigate if magnetocardiographic (MCG) analysis of cardiac micropotentials within the QRS complex can identity patients prone to ventricular arrhythmias, and to compare it to MCG time-domain, late-field analysis. The study population consisted of 136 patients with remote MI, 53 with and 83 without a history of VT. After averaging and high pass filtering of multichannel MCG signals, time-domain parameters describing the end-QRS activity and fragmentation index M and score S describing the whole QRS complex were computed. Fragmentation and time-domain parameters differed between the VT and control groups: fragmentation index M was 12 +/- 3 versus 9 +/- 2 (P <0.001), fragmentation score S was 83 +/- 42 versus 56 +/- 21 (P < 0.001), and filtered QRS duration was 144 +/- 32 versus 114 +/- 19 ms (P < 0.001) in VT and control groups, respectively. A combination of fragmentation parameters yielded 87% sensitivity and 61% specificity in VT identification. Corresponding figures for a time-domain parameter combination were 81% and 72%. Sensitivity of time-domain analysis was 88% and specificity was 75% in a subgroup with anterior MI. In multivariate analysis, fragmentation and time-domain analyses discriminated VT patients from controls independently of the extent of coronary artery disease or left ventricular dysfunction. MCG in postinfarction patients reveals pathology associated with propensity to ventricular arrhythmias inside and not only at the end of the QRS complex. MCG seems most accurate in the anterior infarct location.

Aged↗
PubMed2001

Repolarization abnormalities detected by magnetocardiography in patients with dilated cardiomyopathy and ventricular arrhythmias.

INTRODUCTION: Abnormal repolarization is one of the acknowledged mechanisms leading to malignant ventricular arrhythmias. We used a novel magnetocardiographic technique to investigate the role of inhomogeneous repolarization in patients with nonischemic dilated cardiomyopathy prone to sustained ventricular arrhythmias. METHODS AND RESULTS: Forty-nine dilated cardiomyopathy patients were studied, 18 with a history of sustained ventricular tachycardia (n = 6) or ventricular fibrillation (n = 12) and 31 with no ventricular arrhythmias. The magnetocardiogram was registered and QT apex and QT end intervals were determined by a computer algorithm. Inhomogeneity of repolarization was characterized with indices describing QT apex and QT end dispersion, and T wave end duration. In addition, time-domain late fields of the QRS complex in magnetocardiography and QT dispersion in 12-lead ECG were determined. T wave end was longer in the arrhythmia group in patients with sinus rhythm (87 +/- 15 msec vs 73 +/- 12 msec; P = 0.005) and in those not having bundle branch block. Magnetocardiographic late fields of the QRS complex were not different between groups. QT apex and end dispersion on magnetocardiography or 12-lead ECG showed no difference. CONCLUSION: Prolongation of the end part of the T wave revealed by magnetocardiography is related to malignant ventricular arrhythmias in dilated cardiomyopathy. The results suggest that abnormal repolarization rather than delayed conduction underlies the arrhythmias in this disease.

Adult↗
PubMed2001

Postmyocardial infarction patients susceptible to ventricular tachycardia show increased T wave dispersion independent of delayed ventricular conduction.

INTRODUCTION: Experimentally, both delayed ventricular conduction and nonhomogeneous ventricular repolarization contribute to reentrant arrhythmias. We tested the hypothesis that increased T wave dispersion is independent of delayed ventricular conduction associated with arrhythmia vulnerability in postmyocardial infarction (post-MI) patients. METHODS AND RESULTS: We studied 32 post-MI patients with clinical or inducible monomorphic ventricular tachycardia (VT group), 28 post-MI patients without arrhythmias (MI group), and 13 healthy controls, using magnetocardiographic (MCG) mapping with signal averaging. Twelve-lead ECG was the reference. Filtered QRS duration (fQRS) and T wave peak to T wave end interval (TPE) were used as measures of ventricular conduction and nonhomogeneity in ventricular repolarization, respectively. In MCG, the VT group showed the longest fQRS (135+/-34 msec vs 114+/-22 msec in the MI group; P = 0.012). Mean TPE and maximum TPE in VT versus MI groups were 78+/-9 msec versus 70+/-6 msec (P < 0.001) and 117+/-23 msec versus 104+/-19 msec (P = 0.020), respectively. Maximum TPE did not correlate with fQRS in the VT group (r = 0.063; P = NS) but did correlate in the MI group (r = 0.396; P = 0.037). For identification of post-MI patients prone to VT, selection of cutoff values for fQRS >140 msec and mean TPE >81 msec gave sensitivity and specificity of 41% and 89%, and 31% and 96%, respectively. Their combination increased sensitivity to 63% while maintaining 89% specificity. CONCLUSION: Post-MI patients susceptible to VT show increased T wave dispersion independent of delayed ventricular conduction.

Aged↗
PubMed2001

Current-density estimation of exercise-induced ischemia in patients with multivessel coronary artery disease.

Magnetocardiographic and body surface potential mapping data measured in 6 patients with multivessel coronary artery disease were used in equivalent current-density estimation (CDE). Patient-specific boundary-element torso models were acquired from magnetic resonance images. Positron emission tomography data registrated with anatomical magnetic resonance imaging data provided the gold standard. Discrete current-density estimation values were computed on the epicardial surface of the left ventricle from difference (stress-rest) ST-segment maps. The ill-posed inverse problem was regularized with 3 different methods (Tikhonov regularization with an identity or a surface Laplacian operator and a maximum a posteriori estimator). Comparisons with positron emission tomography studies showed that the maximum a posteriori estimator is superior to other regularizations, provided that a suitable a priori information is available. In general, good correspondence was found for segments of high and low amplitude in current-density estimations, and the viable and scar areas in positron emission tomography, respectively.

Body Surface Potential Mapping↗
PubMed2001

Beat-to-beat analysis method for magnetocardiographic recordings during interventions.

Multichannel magnetocardiography (MCG) during exercise testing has been shown to detect myocardial ischaemia in patients with coronary artery disease. Previous studies on exercise MCG have focused on one or few time intervals during the recovery period and only a fragment of the data available has been utilized. We present a method for beat-to-beat analysis and parametrization of the MCG signal. The method can be used for studying and quantifying the changes induced in the MCG by interventions. We test the method with data recorded in bicycle exercise testing in healthy volunteers and patients with coronary artery disease. Information in all cardiac cycles recorded during the recovery period of exercise MCG testing is, for the first time, utilized in the signal analysis. Exercise-induced myocardial ischaemia was detected by heart rate adjustment of change in magnetic field map orientation. In addition to the ST segment, the T wave in the MCG was also found to provide information related to myocardial ischaemia. The method of analysis efficiently utilizes the spatial and temporal properties of multichannel MCG mapping, providing a new tool for detecting and quantifying fast phenomena during interventional MCG studies. The method can also be applied to an on-line analysis of MCG data.

Coronary Disease↗
PubMed2001

In vitro evaluation of frozen-thawed stallion semen: a review.

The article reviews methods used for in vitro evaluation of sperm, with particular emphasis on frozen-thawed stallion sperm. The techniques, limitations of the methods and correlations with fertility results are discussed. Very few studies have tried to find correlation between fertility of frozen stallion semen and laboratory tests. It is difficult and expensive to inseminate an adequate number of mares to achieve statistically significant differences. Significant, but low correlations have been demonstrated between the foaling rate and subjective motility of sperm incubated for 2 h and 4 h at 37 degrees C and hypoosmotic swelling test after 0 and 3 h of incubation. Significant correlations have been reported between the pregnancy rate and viability of propidium iodide-stained sperm assessed by flow cytometry as well as for glass wool and Sephadex filtration tests. No correlations have been detected between fertility and motility immediately after thawing. In spite of that, motility estimation by light microscope is the most commonly used method to evaluate frozen-thawed stallion sperm. Computer assisted automatic sperm analyzers have replaced light microscopy in research projects, but so far nobody has been able to demonstrate a correlation between fertility of frozen stallion semen and any of the motility parameters obtained by these instruments.

Animals↗
PubMed2000

Administration of gonadotropin-releasing hormone during metoestrus in cattle: influence on luteal function and cycle length.

Gonadotropin-releasing hormone (GnRH) has been used to warrant the success of artificial insemination by accurately timing occurrence of ovulation. In practical conditions, GnRH may be administered too late, after ovulation, with an eventual reduction in pregnancy rate. The aim of this study was to investigate whether GnRH administration after ovulation would have a negative effect on luteal function. Three cows and six heifers of the Finnish Ayrshire breed were used. Oestruses were synchronised. After detection of ovulation, one of the following treatments was implemented: gonadorelin (250 microg, i.m.) at either 0-24h (T1) or 24-48h (T2) post-ovulation or control (no gonadorelin, C). Every animal was assigned once to each of these three manipulations. Ultrasonography was performed on days 1, 4 or 5, 7 or 8, 11 or 12, 14 or 15 post-ovulation and daily from the beginning of the next oestrous signs until ovulation (day 0=day of ovulation). Blood samples for progesterone (P(4)) determinations were collected daily from day 1 after the occurrence of ovulation until recording of the next oestrus. Administration of GnRH during metoestrus did not induce ovulation of either large or small follicles and, thus, no accessory corpora lutea (CL) were formed. In T1, on day 14 or 15, the diameter of CL was 1.3+/-0.3mm smaller than in C (P<0.01), but no differences were found either on days 11 or 12 or on the same days of the T2 and C treatments. No significant differences in levels or profiles of P(4) curves were found between GnRH treatments and control. Neither had the treatments any effects on the length of the oestrous cycle. In conclusion, GnRH treatment during metoestrus does not seem to alter subsequent luteal function and, thus, this does not explain previous reports of reduced fertility post-treatment.

Animals↗
PubMed2000

T-cell distribution in two different segments of the equine endometrium 6 and 48 hours after insemination.

The T-cell response after the introduction of semen into the uterine cavity in the mare was studied by examining, immunohistochemically, the distribution of helper T-cells (CD4+) and cytotoxic T-cells (CD8+) in endometrial biopsy specimens. Endometrial tissue samples were obtained from twenty-five gynecologically healthy mares during estrus before and 6 or 48 h after deposition of a single dose of stallion semen. An increase (P=0.04) in the number of helper T-cells (CD4+) compared to pre-insemination values was observed in the uterine body in both groups, 6 and 48 h, after insemination. No significant variations in numbers of CD8+ cells were recorded either 6 or 48 h after insemination. There seems to be an early (6 h) recruitment of helper T-cells to the equine endometrium after semen deposition, which might be related to the activation of the endometritis-like reaction seen as part of the equine uterine immune defense during estrus.

Animals↗
PubMed2000

Identification of post-myocardial infarction patients with ventricular tachycardia by time-domain intra-QRS analysis of signal-averaged electrocardiogram and magnetocardiogram.

A new time-domain analysis method, which quantifies ECG/MCG intra-QRS fragmentation, is applied to parts of the QRS complex to identify post-myocardial infarction patients with ventricular tachycardia. Three leads of signal-averaged electrocardiograms and nine leads of magnetocardiograms were band-pass filtered (74 Hz to 180 Hz). The filtered signals showed fragmentation in the QRS region, which was quantified by the number of peaks M and a score S, that is the product of M and the sum of the peak amplitudes. Both parameters were determined for the first 80 ms of the QRS complex and the total QRS complex in each channel. For classification, the mean-values of the parameters M and S of the three electrical leads and the nine magnetic leads were calculated. Late potential and late field analyses were performed for the same signals. 31 myocardial infarction patients were included, 20 of them with a history of documented ventricular tachycardia (VT). Identification of VT patients using the SAECG led to better results (sensitivity 95%, specificity 91%) considering the entire QRS complex than with the standard late potential analysis suggested by Simson (sensitivity 90%, specificity 73%). For the SAMCG and the entire QRS complex results using the parameters S and M are also better (sensitivity 95%, specificity 100%) than for the late field analysis (sensitivity 90% and specificity 100%). For the first 80 ms, the performance of the parameters M and S is only slightly decreased.

Adult↗
PubMed2000

Conversion of magnetocardiographic recordings between two different multichannel SQUID devices.

Comparison of biomagnetic measurements performed with different multichannel magnetometers is difficult, because differing sensor types and locations do not allow measurements from the same locations in respect to the body. In this study, two transformation procedures were utilized to compare magnetocardiograms (MCG) recorded with two different multisensor systems. Signals from one sensor array were used to compute parameters of a multipole expansion or minimum-norm estimates at 1-ms steps over the cardiac cycle. The signals of the second sensor array were then simulated from the computed estimates and compared against measured data. Both the multipole- and the minimum-norm-based transformation method yielded good results; the average correlation between simulated and measured signals was 93%. Thus, the methods are useful to compare MCG recordings performed using differing sensor configurations, e.g., for multicenter patient studies. This study provides the first empirical basis for assessing the transformation of MCG data of differing devices by general model-based field reconstructions.

Biomedical Engineering↗
PubMed2000

The effect of geometric and topologic differences in boundary element models on magnetocardiographic localization accuracy.

This study was performed to evaluate the changes in magnetocardiographic (MCG) source localization results when the geometry and the topology of the volume conductor model were altered. Boundary element volume conductor models of three patients were first constructed. These so-called reference torso models were then manipulated to mimic various sources of error in the measurement and analysis procedures. Next, equivalent current dipole localizations were calculated from simulated and measured multichannel MCG data. The localizations obtained with the reference models were regarded as the "gold standard." The effect of each modification was investigated by calculating three-dimensional distances from the gold standard localizations to the locations obtained with the modified model. The results show that the effect of the lungs and the intra-ventricular blood masses is significant for deep source locations and, therefore, the torso model should preferably contain internal inhomogeneities. However, superficial sources could be localized within a few millimeters even with nonindividual, so called standard torso models. In addition, the torso model should extend long enough in the pelvic region, and the positions of the lungs and the ventricles inside the model should be known in order to obtain accurate localizations.

Biomedical Engineering↗
PubMed2000

Late fields of the magnetocardiographic QRS complex as indicators of propensity to sustained ventricular tachycardia after myocardial infarction.

INTRODUCTION: Magnetocardiographic (MCG) mapping is a new method to record cardiac signals. This study examined the association of MCG late fields with the propensity to sustained ventricular tachycardia (VT) after myocardial infarction (MI). METHODS AND RESULTS: One hundred patients with remote MI were studied, 38 with and 62 without history of VT. High-resolution MCG and signal-averaged ECG (SAECG) as a comparative method were recorded. Time-domain parameters describing the abnormal low-amplitude end QRS activity, MCG late fields, and SAECG late potentials were analyzed. Late field parameters differed significantly between the patient groups: filtered QRS duration was 137 +/- 26 msec in the VT group and 110 +/- 18 msec in the control group (P < 0.001), and root mean square amplitude of the last 40 msec was 260 +/- 170 and 510 +/- 360 fT (P < 0.001), respectively. The optimal MCG parameter combination yielded a sensitivity of 92% and a specificity of 61% in classification to the VT group, whereas those for SAECG were 63% and 66%. In a subgroup of 63 patients with marked left ventricular dysfunction and comparable stage of coronary heart disease, only MCG (sensitivity 73%, specificity 67%) but not SAECG could assign a patient to the VT group. CONCLUSION: Late fields of the MCG QRS complex indicate propensity to life-threatening arrhythmias in post-MI patients. This discriminative ability persists in the presence of severe left ventricular dysfunction where ECG late potentials lose their informative value. MCG late field analysis is a potential new method for noninvasive risk assessment in post-MI patients.

Electrocardiography↗
PubMed1999

Quality of stallion semen obtained by a new semen collection phantom (Equidame) versus a Missouri artificial vagina.

A study was performed to test a new semen collection device (Equidame phantom) that fractionates the ejaculate by comparing the quality of semen obtained by the Equidame phantom with that obtained by a Missouri artificial vagina. Semen from 4 Finnhorse stallions was collected 4 times per stallion by both methods. Half of the ejaculate was frozen and the other half extended and loaded into 2 Equitainer transport containers (24- and 48-h samples). Motility parameters were determined by a Hamilton-Thorn motility analyzer after cooled storage for 24 and 48 h and again after freezing/thawing. Raw and chilled semen samples were cultured and the number of bacterial colonies counted after incubations of 24 and 48 h. After a 24-h incubation the number of colony-forming units (CFU) in raw semen was significantly higher (P<0.01) when collected by the Missouri artificial vagina than by the Equidame phantom. After cooled storage, 75% of the semen samples contained no bacteria after an incubation of 24 h, and 69% yielded no growth after 48 h. The sperm-rich fractions (Cup 2) collected by the Equidame phantom had lower mean volumes (22.1 +/- 2.3 mL [+/- SEM] versus 101.6 +/- 9.3 mL) and significantly higher mean sperm concentrations (218.0 +/- 25.8 x 10(6) vs 86.2 +/- 8.1 x 10(6) cells/mL; P<0.05) than the total ejaculates collected by the Missouri device. The total and progressive motility of chilled and frozen-thawed semen did not differ significantly between collection methods. The Equidame phantom yielded semen that was of a lower bacteriological colony counts, but had sperm motility similar to that of semen collected with the traditional method by the Missouri artificial vagina.

Animals↗
PubMed1999

Induction of ovulation with gonadotropin-releasing hormone during proestrus in cattle: influence on subsequent follicular growth and luteal function.

Induction of ovulation by administration of gonadotropin-releasing hormone (GnRH) is commonly practiced in cattle to treat repeat breeders or cows exhibiting long estrous periods. This treatment may, however, disturb normal reproductive functions if timing is incorrect. The objective of the present study was to investigate the effect of exogenous GnRH on estradiol secretion of the ovulatory follicle, occurrence of ovulation, development and function of the corpus luteum (CL) and growth of a dominant follicle after ovulation in the bovine, when GnRH treatment was given before the expected physiological LH-surge. Luteolysis was induced by cloprostenol (PG) in three cows and six heifers. Every animal was assigned once to each of the following treatment or control manipulations, receiving either a single dose (0.1 mg) of GnRH (gonadorelin) at (1) 24 h (T1), (2) 48 h (T2), or (3) 72 h (T3) after PG, or (4) no gonadorelin (control manipulation, C). Ovaries were scanned by ultrasound and blood samples were collected for progesterone (P4) and estradiol-17beta (E-17beta) determination. Growth curves of dominant follicles between treatment I and the control differed significantly (P < 0.01). One day after ovulation, the diameter of the dominant follicle was almost 1 mm larger in T1. This difference remained almost unchanged during the entire follow-up period. The recruitment of a new follicular wave after ovulation seemed to occur earlier. Development of CL and levels and profiles of P4-production remained unaffected. When GnRH was given 1 day after PG injection, two animals showed significantly different development of CL (P < 0.05) and of P4-production (both in concentrations [P < 0.05] and profile [P < 0.01]). After normal ovulation and CL development, luteolysis took place on days 5 or 6 after ovulation, and animals ovulated on days 9 and 10. It is suggested that early induction of ovulation with GnRH can cause shortened luteal function in cattle and, ultimately, reduced fertility.

Animals↗
PubMed1999

Multichannel magnetocardiographic measurements with a physical thorax phantom.

Artificial dipolar sources were applied inside a physical thorax phantom to experimentally investigate the accuracy obtainable for non-invasive magnetocardiographic equivalent current dipole localisation. For the measurements, the phantom was filled with saline solution of electrical conductivity 0.21 S m-1. A multichannel cardiomagnetometer was employed to record the magnetic fields generated by seven dipolar sources at distances from 25 mm to 145 mm below the surface of the phantom. The inverse problem was solved using an equivalent current dipole in a homogeneous boundary element torso model. The dipole parameters were determined with a non-linear least squares fitting algorithm. The signal-to-noise ratio (SNR) and the goodness of fit of the calculated localisations were used in assessing the quality of the results. The dependence between the SNR and the goodness of fit was derived, and the results were found to correspond to the model. With SNR between 5 and 10, the average localisation error was found to be 9 +/- 8 mm, while for SNR between 30 and 40 and goodness of fit between 99.5% and 100%, the average error reduced to 3.2 +/- 0.3 mm. The SNR values obtained in this study were also compared with typical clinical values of SNR.

Cardiology↗