Comparison between a time-domain and a frequency-domain system for optical tomography.

The quality of phase and amplitude data from two medical optical tomography systems were compared. The two systems are a 32-channel time-domain system developed at University College London (UCL) and a 16-channel frequency-domain system developed at Helsinki University of Technology (HUT). Difference data measured from an inhomogeneous and a homogeneous phantom were compared with a finite-element method (diffusion equation) and images of scattering and absorption were reconstructed based on it.

QRS duration in high-resolution methods and standard ECG in risk assessment after first and recurrent myocardial infarctions.

Background: Prolonged QRS duration (QRSd) is associated with increased mortality after myocardial infarction (MI). Only little data exist about its predictive ability and relationships to clinical variables in the present era of active treatment of myocardial ischemia and cardiac dysfunction. We investigated whether QRSd in high-resolution methods and standard ECG predict arrhythmic events and cardiac death in post-infarction patients with cardiac dysfunction and how it relates to clinical variables, with a special emphasis on history of previous MI.

Magnetocardiographic assessment of healed myocardial infarction.

Background: We evaluated the capability of multichannel magnetocardiography (MCG) to detect healed myocardial infarction (MI).

Methods: Multichannel MCG over frontal chest was recorded at rest in 21 patients with healed MI, detected by cine- and contrast-enhanced magnetic resonance imaging, and in 26 healthy controls. Of the 21 MI patients, 11 had non-Q wave and 10 Q wave MIs.

Increased intra-QRS fragmentation in magnetocardiography as a predictor of arrhythmic events and mortality in patients with cardiac dysfunction after myocardial infarction.

Introduction: Increased intra-QRS fragmentation score (FRA) in magnetocardiography (MCG) has shown association with sustained ventricular arrhythmias in post-MI patients suggesting its relation to arrhythmia substrate. The aim of this study was to investigate whether increased FRA in MCG predicts arrhythmic events and mortality after acute myocardial infarction (MI) with cardiac dysfunction.

Methods And Results: A series of 158 patients with acute MI and left ventricular ejection fraction (LVEF) <50% were studied.

Bilateral hemodynamic responses to auditory stimulation in newborn infants.

We studied hemodynamic auditory evoked responses of 20 healthy full-term neonates with near-infrared spectroscopy. The instrument used allows the measurements to be performed simultaneously above both auditory cortices. The stimulation consisted of 5-s trains of sound (700-ms interstimulus interval) with a 25-s silent interval.

Spatial repolarization abnormalities in old myocardial infarction.

Conventional electrocardiogram criteria for myocardial infarction (MI) rely on QRS features, but ST-T segment is also affected. We recorded body surface potential mapping in 24 patients with prior MI and in 24 controls. T-wave maximum amplitude and QRS and ST-T integrals were automatically determined.

Vortex shaped current sources in a physical torso phantom.

Recent studies reported differential information in human magnetocardiogram and in electrocardiogram. Vortex currents have been discussed as a possible source of this divergence. With the help of physical phantom experiments, we quantified the influence of active vortex currents on the strength of electric and magnetic signals, and we tested the ability of standard source localization algorithms to reconstruct vortex currents.

Temporal analysis of the depolarization wave of healed myocardial infarction in body surface potential mapping.

Background: We studied the ability of different time segments of the depolarization wave recorded with body surface potential mapping (BSPM) to detect and localize myocardial infarction (MI).

Methods: BSPM was recorded in 24 patients with remote MI and in 24 healthy controls. Cine and contrast-enhanced magnetic resonance imaging (MRI) was used as a reference method.

Spatiotemporal characterization of paced cardiac activation with body surface potential mapping and self-organizing maps.

In this study self-organizing maps (SOM) were utilized for spatiotemporal analysis and classification of body surface potential mapping (BSPM) data. Altogether 86 cardiac depolarization (QRS) sequences paced by a catheter in 18 patients were included. Spatial BSPM distributions at every 5 ms over the QRS complex were first presented to an untrained SOM.

A 3-D model-based registration approach for the PET, MR and MCG cardiac data fusion.

In this paper, a new approach is presented for the assessment of a 3-D anatomical and functional model of the heart including structural information from magnetic resonance imaging (MRI) and functional information from positron emission tomography (PET) and magnetocardiography (MCG). The method uses model-based co-registration of MR and PET images and marker-based registration for MRI and MCG. Model-based segmentation of MR anatomical images results in an individualized 3-D biventricular model of the heart including functional parameters from PET and MCG in an easily interpretable 3-D form.

ST-T integral and T-wave amplitude in detection of exercise-induced myocardial ischemia evaluated with body surface potential mapping.

Body surface potential mapping is superior to 12-lead electrocardiogram in detection of acute and old myocardial infarctions. We examined the capability of the ST-T integral and T wave to detect exercise-induced ischemia in body surface potential mapping. Body surface potential mapping with 123 channels was recorded in 70 subjects: 45 coronary artery disease (CAD) patients and 25 healthy controls during supine bicycle exercise testing.

A review of cardiac image registration methods.

In this paper, the current status of cardiac image registration methods is reviewed. The combination of information from multiple cardiac image modalities, such as magnetic resonance imaging, computed tomography, positron emission tomography, single-photon emission computed tomography, and ultrasound, is of increasing interest in the medical community for physiologic understanding and diagnostic purposes. Registration of cardiac images is a more complex problem than brain image registration because the heart is a nonrigid moving organ inside a moving body.

Late QRS activity in signal-averaged magnetocardiography, body surface potential mapping, and orthogonal ECG in postinfarction ventricular tachycardia patients.

Background: Delayed electrical activity necessary for re-entrant ventricular tachycardia (VT) is detectable noninvasively with high resolution techniques. We compared high resolution signal-averaged analysis of magnetocardiography (MCG), body surface potential mapping (BSPM), and orthogonal three-lead ECG (SA-ECG) in the identification of patients prone to VT after myocardial infarction (MI).

Methods: Patients with remote myocardial infarction and cardiac dysfunction were studied, 22 with (VT group) and 22 without VT (control group).

Magnetocardiographic indices of left ventricular hypertrophy.

Objective: We tested the hypothesis that multichannel magnetocardiographic (MCG) mapping can detect and quantify the degree of left ventricular hypertrophy (LVH).

Design: A cross-sectional study.

Setting: Helsinki University Central Hospital, a tertiary referral center.

Relation of magnetocardiographic arrhythmia risk parameters to delayed ventricular conduction in postinfarction ventricular tachycardia.

Time-domain late field and intra-QRS fragmentation parameters in magnetocardiography (MCG) identify patients prone to VT after myocardial infarction. This study investigated if they are related to slow ventricular conduction and affected by arrhythmia surgery. Twenty-two patients with old myocardial infarction undergoing map-guided subendocardial resection to treat sustained VT were included.

Features of ST segment and T-wave in exercise-induced myocardial ischemia evaluated with multichannel magnetocardiography.

Background And Aim: Magnetocardiography (MCG) is a novel, non-contact mapping technique to record cardiac magnetic field. We evaluated MCG criteria for myocardial ischemia in stress testing.

Methods: Multichannel MCG over frontal chest was performed in 44 patients with coronary artery disease (CAD) and 26 healthy controls during supine bicycle exercise test.