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38 results on '"Montonen, Juha"'

1. Intelligent digital tools for screening of brain connectivity and dementia risk estimation in people affected by mild cognitive impairment: the AI-Mind clinical study protocol

Author

Haraldsen, Ira H., primary, Hatlestad-Hall, Christoffer, additional, Marra, Camillo, additional, Renvall, Hanna, additional, Maestú, Fernando, additional, Acosta-Hernández, Jorge, additional, Alfonsin, Soraya, additional, Andersson, Vebjørn, additional, Anand, Abhilash, additional, Ayllón, Victor, additional, Babic, Aleksandar, additional, Belhadi, Asma, additional, Birck, Cindy, additional, Bruña, Ricardo, additional, Caraglia, Naike, additional, Carrarini, Claudia, additional, Christensen, Erik, additional, Cicchetti, Americo, additional, Daugbjerg, Signe, additional, Di Bidino, Rossella, additional, Diaz-Ponce, Ana, additional, Drews, Ainar, additional, Giuffrè, Guido Maria, additional, Georges, Jean, additional, Gil-Gregorio, Pedro, additional, Gove, Dianne, additional, Govers, Tim M., additional, Hallock, Harry, additional, Hietanen, Marja, additional, Holmen, Lone, additional, Hotta, Jaakko, additional, Kaski, Samuel, additional, Khadka, Rabindra, additional, Kinnunen, Antti S., additional, Koivisto, Anne M., additional, Kulashekhar, Shrikanth, additional, Larsen, Denis, additional, Liljeström, Mia, additional, Lind, Pedro G., additional, Marcos Dolado, Alberto, additional, Marshall, Serena, additional, Merz, Susanne, additional, Miraglia, Francesca, additional, Montonen, Juha, additional, Mäntynen, Ville, additional, Øksengård, Anne Rita, additional, Olazarán, Javier, additional, Paajanen, Teemu, additional, Peña, José M., additional, Peña, Luis, additional, Peniche, Daniel lrabien, additional, Perez, Ana S., additional, Radwan, Mohamed, additional, Ramírez-Toraño, Federico, additional, Rodríguez-Pedrero, Andrea, additional, Saarinen, Timo, additional, Salas-Carrillo, Mario, additional, Salmelin, Riitta, additional, Sousa, Sonia, additional, Suyuthi, Abdillah, additional, Toft, Mathias, additional, Toharia, Pablo, additional, Tveitstøl, Thomas, additional, Tveter, Mats, additional, Upreti, Ramesh, additional, Vermeulen, Robin J., additional, Vecchio, Fabrizio, additional, Yazidi, Anis, additional, and Rossini, Paolo Maria, additional

Published
2024
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2. Standardisation of available and prospective data collection

Author

Liljeström, Mia, Renvall, Hanna, Kinnunen, Antti, Mäntynen, Ville, Montonen, Juha, Hattlestad-Hall, Christoffer, Ramírez, Federico, Maestú, Fernando, Marra, Camillo, Miraglia, Francesca, Rossini, Paolo Maria, Vecchio, Fabrizio, Haraldsen, Ira, and Cruz, Andreia

Subjects
Artificial intelligence, Electrocardiography, Mild Cognitive Impairment, Magnetoencephalography, Dementia, Alzheimer's disease
Abstract

This deliverable describes the shared requirements, technical solutions, and methods for collecting clinical data at the AI-Mind clinical partner sites. For that purpose, we define protocols for using research devices, materials, and clinical data handling practises to be implemented at all prospective participant visits. The clinical data will be collected at five sites in four countries (Oslo University Hospital (OUS), Oslo, Norway; Helsinki University Hospital (HUH), Helsinki, Finland; Scientific Institute for Research, Hospitalization and Healthcare, San Raffaele Roma (IRCSS) and Università Cattolica del Sacro Cuore (UCSC), Rome, Italy; Complutense University of Madrid (UCM), Madrid, Spain). The scope of this deliverable spans from acquiring the EEG/MEG data, digital cognitive testing, blood samples, and textual data from questionnaires and neuropsychological testing (NPT), to managing the (pseudonymised) clinical data at the respective sites. These protocols apply to all the clinical partners; MEG protocols will be implemented only in UCM and HUH. The AI Mind project handles both prospective (to be collected) and retrospective data (acquired earlier for other clinical and scientific purposes and included in the data transfer agreements (DTA) between the clinical sites). The emphasis of this deliverable is on the handling prospective data, but it will also define the minimum common requirements for the data handling protocols of the retrospective EEG data at the respective sites. Harmonisation of retrospective data will be further discussed in Deliverable D2.3, where also the preprocessing protocols for all the clinical MEG/EEG data are defined.

Published
2022
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10. Transformation of multichannel magnetocardiographic signals to standard grid form

Author

Numminen, Jussi, Ahlfors, Seppo, Ilmoniemi, Risto, Montonen, Juha, and Nenonen, Jukka

Subjects
Biomagnetism -- Research, Magnetometer -- Research, Biological sciences, Business, Computers, Health care industry
Abstract

Multichannel magnetocardiographic (MCG) recordings with fixed sensor arrays are not directly comparable with single-channel measurements carried out at standard grid locations. In addition, comparison of data obtained with different types of magnetometers is difficult. We present a method for transforming multichannel measurements to the standard-grid format. The minimum-norm estimate (MNE) of the source current distribution in the body is calculated, and the desired field components in standard grid points are then computed from the MNE. We measured three subjects with both a 24-channel and a single-channel instrument. The signals extrapolated from the multichannel measurements corresponded quite well to the single-channel data registered at the standard grid locations, especially in those grid points that were covered by the 24-channel device. The signal-amplitude-weighted correlations between the extrapolated and directly measured signals were 0.73-0.87. In simulations with ideal measurement geometry but with a realistic amount of random noise in the signals, we obtained a 0.99 correlation. It was also found that the method is relatively tolerant to errors in the location and orientation of the multichannel magnetometer. For example, a simulated 20-mm displacement in the location of the sensor array caused only a 3% decrease in the correlation, and when it was rotated and tilted by 10 [degrees], the correlation decreased by 5%. The basic advantage of our extrapolation method is its physiologic nature: the method is based on the mathematical modeling of the source current distribution, rather than on direct constraints applied to the magnetic field.

Published
1995

12. Spatial and temporal methods for analysing magnetocardiographic mappings of the atrial activity

Author

Montonen, Juha, Nenonen, Jukka, Teknillinen korkeakoulu, Helsinki University of Technology, Teknillisen fysiikan ja matematiikan osasto, Katila, Toivo, Mäntynen, Ville, Montonen, Juha, Nenonen, Jukka, Teknillinen korkeakoulu, Helsinki University of Technology, Teknillisen fysiikan ja matematiikan osasto, Katila, Toivo, and Mäntynen, Ville

Abstract

Atrial fibrillation (AF) is the most common arrhythmia of the heart requiring hospitalization. AF is not generally fatal, but it heavily increases the risk of thrombi (blood cloth). Symptoms of AF have been reported to significantly reduce the quality of life. Several cardiovascular diseases expose to AF. However, approximately quarter of the patients (lone AF) have no cardiac or other underlying disease. In this thesis, methods were studied and created to examine the human atria using especially magnetocardiography (MCG). The work is a part of a research line that includes also the MCG measurements at the BioMag laboratory located at the Helsinki University Central Hospital. The subject matter of the thesis is three-fold: The software for MCG-measurements was modified, and different noise suppression methods were presented. Especially two noise-model based adaptive filters were compared. The filters may be used to suppress the power-line interference in bio magnetic recordings. A method for multichannel time alignment based on pattern recognition was developed utilizing correlations between waveforms. The method can be used to time align the atrial and ventricular waves independently in bio magnetic recordings. The accuracy of the method was found to be good. Magnetic multipole expansion was used to interpolate the MCG mappings for visualisation and gradient analysis. Previously used to analyse the ventricular activation, the gradient analysis of the MCG mappings was applied to study and parameterize the atrial activation. Through the gradient analysis it is also possible to create so-called pseudo-current map that describes the current induced by the heart in the human body. During this work it was also found that it is quite common that the atrial waves present two or even three different morphologies in the mappings of both patients and healthy volunteers. Changes in the signal morphology suggest different conduction pathways in the atria. In addition, it seems, Sydämen eteisvärinä (EV) on yleisin sairaalahoitoa vaativa rytmihäiriö. EV ei yleensä johda kuolemaan, mutta se lisää voimakkaasti tromboembolisaatioiden (veritulppa) riskiä. Taudin aiheuttamat oireet sekä sairauden tuntemukset laskevat elämän laatua selvästi. Monien sydän- ja verisuonisairauksien on havaittu altistavan eteisvärinälle. Kuitenkaan neljänneksellä potilaista ei todeta EV:n lisäksi muuta sydänsairautta tai altistavaa syytä (idiopaattinen EV). Tässä työssä tutkittiin ja kehitettiin menetelmiä sydämen eteisten toiminnan tutkimiseksi erityisesti magnetokardiogrammin (MKG) avulla. Työ on osa eteisvärinäalttiuden arviointiin keskittyvää hanketta, johon kuuluvat myös MKG-mittaukset Helsingin Yliopistollisessa Keskussairaalassa sijaitsevassa BioMag-laboratoriossa. Työn aihepiiri jakautuu kolmeen osa-alueeseen: Työssä muokattiin MKG-mittausohjelmistoa sekä esiteltiin käytössä olevia ja käyttöön tulevia häiriönpoistomenetelmiä. Erityisesti verrattiin kahta häiriömalliin perustuvaa suodinta, joita voidaan käyttää biosähkömagneettisissa mittauksissa toisinaan esiintyvien verkkovirtahäiriöiden vähentämiseen. Aaltomuotojen korrelaation avulla luotiin hahmontunnistukseen perustuva monikanavainen sydänsignaalin aaltomuotojen ajoitusmenetelmä, jolla voidaan ajoittaa kammiokompleksien lisäksi myös eteisaallot toisistaan riippumatta. Menetelmän ajoitustarkkuuden havaittiin olevan hyvä. Työssä käytettiin magneettista muitipolikehitelmää MKG-kartoitusten interpoloimisessa visualisointia sekä gradienttianalyysia varten. Aiemmin kammioaktivaation tutkimiseen käytettyä MKG-kartoituksen gradienttianalyysia sovellettiin eteisaaltojen parametrisoinnissa. Gradienttianalyysin avulla voidaan tuottaa myös nk. pseudovirtakartta, joka kuvaa sydämen toiminnan aiheuttamaa virtaa kehossa. Työn aikana havaittiin, että eteisaaltojen morfologia vaihtelee sekä potilailla että terveillä kahden tai jopa kolmen muodon välillä ilman liukumaa. Morfologiamuutokset viittaavat aktivaation johtumisre

Published
2004

21. Exercise ergometer in cardiomagnetic measurements

Author

Montonen, Juha, Teknillinen korkeakoulu, Helsinki University of Technology, Teknillisen fysiikan ja matematiikan osasto, Katila, Toivo, Takala, Panu, Montonen, Juha, Teknillinen korkeakoulu, Helsinki University of Technology, Teknillisen fysiikan ja matematiikan osasto, Katila, Toivo, and Takala, Panu

Abstract

Sydänlihaksen solujen yhdenaikaisen aktivaation seurauksena sydämessä esiintyy biosähköisiä virtoja, jotka synnyttävät heikon magneettikentän kehoon ja sen ulkopuolelle. Magnetokardiografialla (MKG) tarkoitetaan tämän magneettikentän mittaamista kehon ulkopuolelta ja kentän muutosta ajan kuluessa kutsutaan magnetokardiogrammiksi. Rasituksen aikana tehtyjä MKG-mittauksia käsitteleviä tutkimuksia on julkaistu vain vähän. Tehdyt tutkimukset ovat kohdistuneet terveisiin koehenkilöihin eikä yhtään potilasmittausta ole raportoitu. Yksi syy tähän on kaupallisesti saatavan, tarkoitukseen soveltuvan rasitusergometrin puuttuminen. Tavanomaisissa ergometreissä olevien magneettisten osien aiheuttamat häiriöt tekevät sydämen tuottaman heikon magneettikentän rekisteröinnin mahdottomaksi rasituksen aikana. Tässä työssä rakennettiin rasitusergometri, jolla suoritettavan rasituskokeen yhteydessä voidaan rekisteröidä tutkittavan henkilön magnetokardiogrammi. Laitteen keskeisin piirre on, ettei se sisällä magneettisia osia. Ergometri kalibroitiin ja sillä tehtiin rasituskokeita yhteensä kymmenellä potilaalla ja terveellä koehenkilöllä. Mittauksissa rekisteröitiin tutkittavien magnetokardiogrammi, 12-kytkentäinen elektrokardiogrammi (EKG) sekä sähköiset pintapotentiaalit rasituksen aikana. Työssä tehtiin myös MKG-mittausten alustava analysointi. Tehdyt rasituskokeet osoittivat, että myös liikuntaan tottumattomat ja huonokuntoiset potilaat pystyvät suorittamaan rasituskokeen ergometrillä. Kokeissa ergometri toimi ongelmitta eikä yhtään koetta jouduttu keskeyttämään tai peruuttamaan ergometristä johtuvista syistä. Mitatussa MKG-signaalissa ei havaittu ergometrin aiheuttamia häiriöitä. Mittausdatan alustavan analyysin perusteella voidaan todeta sydänlihaksen iskemian olevan havaittavissa rasituksen aikaisella MKG-mittauksella. Vasemman sepelvaltimon ahtaumasta (LAD) kärsivistä potilaista puolella nähtiin välittömästi rasituksen jälkeen mitatun MKG:n ST-väliltä muodostetussa keskiarvokarta

Published
1997

22. Magnetocardiographic indices of left ventricular hypertrophy

Author

Karvonen, Milla, primary, Oikarinen, Lasse, additional, Takala, Panu, additional, Kaartinen, Maija, additional, Rossinen, Juhani, additional, Hänninen, Helena, additional, Montonen, Juha, additional, Nenonen, Jukka, additional, Mäkijärvi, Markku, additional, Keto, Pekka, additional, Toivonen, Lauri, additional, Nieminen, Markku S, additional, and Katila, Toivo, additional

Published
2002
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30. Noninvasive Risk Modeling After Myocardial Infarction * *This study was supported in part by Deutsche Forschungsgemeinschaft (DFG), Förderkennzeichen Br 759/2–2, Bonn; Bundesministerium für Forschung und Technologie (BMFT), Förderkennzeichen HKP314, Bonn; Deutscher Akademischer Austauschdienst (DAAD), Bonn, Germany; Academy of Finland (SA), Helsinki, Finland; European Union Human Capital and Mobility Programme (BIRCH-European Large Scale Facility in Biomagnetic Research at Helsinki University of Technology), Brussels, Belgium; and Franz-Loogen-Stiftung for Cardiological Research, Düsseldorf, Germany

Author

Reinhardt, Lutz, primary, Mäkijärvi, Markku, additional, Fetsch, Thomas, additional, Schulte, Gerrit, additional, Sierra, Gilberto, additional, Martínez-Rubio, Antoni, additional, Montonen, Juha, additional, Katila, Toivo, additional, Borggrefe, Martin, additional, and Breithardt, Günter, additional

Published
1996
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36. Late Fields of the Magnetocardiographic QRS Complex as Indicators of Propensity to Sustained Ventricular Tachycardia after Myocardial Infarction.

Author

Korhonen, Petri, Montonen, Juha, Mäkijärvi, Markku, Katila, Toivo, Nieminen, Markku S., and Toivonen, Lauri

Subjects
HEART disease diagnosis, MYOCARDIAL infarction, VENTRICULAR tachycardia, CARDIOVASCULAR system, CARDIOGRAPHY, ELECTROPHYSIOLOGY
Abstract

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-Ml patients. [ABSTRACT FROM AUTHOR]

Published
2000
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37. Detection of Exercise-Induced Myocardial Ischemia by Multichannel Magnetocardiography in Single Vessel Coronary Artery Disease.

Author

Hänninen, Helena, Takala, Panu, Mäkijärvi, Markku, Montonen, Juha, Korhonen, Petri, Oikarinen, Lasse, Nenonen, Jukka, Katila, Toivo, and Toivonen, Lauri

Abstract

Background: Detection of myocardial ischemia was studied with multichannel exercise magneto-cardiography (MCG). A surface gradient method was applied to analyze cardiac magnetic fields. Methods: We studied 27 patients with single vessel coronary artery disease (CAD) and 17 healthy volunteers. The MCG was recorded over anterior chest during supine bicycle ergometry. The two-dimensional direction of the maximum spatial magnetic field gradient was determined during the ST segment and at the T-wave apex at different phases of stress test. Results: The CAD patient group was separated from controls by the orientation of the magnetic field gradient during the ST segment at cessation of exercise (CAD 167 ± 68° vs controls 106 ± 49°; P < 0.005) and at 4 minutes postexercise, but not at rest. The-CAD patient group was separated from controls also by the orientation of the magnetic field gradient at the T-wave apex at 4 minutes postexercise (CAD 87 ± 60° vs controls 58 ± 18° P < 0.05), but not at rest. The change in the orientation of the field gradient at the T-wave apex 4 minutes postexercise, compared to baseline, was greater in CAD patients (31 ± 43°) than in controls (9 ± 8° P < 0.05). This change was larger in the patient group with stenosis in the right than in the left coronary artery (P < 0.05). Conclusions: Transient acute myocardial ischemia causes well-recognizable changes in the magnetocardiogram at the ST segment and the T wave. The orientation of the maximum spatial gradient of the magnetic field can be used as a parameter to determine these changes. [ABSTRACT FROM AUTHOR]

Published
2000
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