Biomedical subjects

T Trieb

Publications and source records attributed to T Trieb.

7 recordsLinked to original sources

PubMed2006

Evaluation of transient apical ballooning with cardiac magnetic resonance imaging and 31-phosphorous magnetic resonance spectroscopy.

Apical ballooning is an increasingly reported transient cardiomyopathy with yet unknown origin. In this study 2 cases of apical ballooning are described in whom we used a combined approach of cardiac magnetic resonance imaging (CMR) and 31-Phosphorous magnetic resonance spectroscopy (31P MRS). Electrocardiogram showed ST abnormalities and cardiac serum markers were mildly elevated, but CAG demonstrated smooth coronary arteries. Cine-CMR revealed severe apical akinesia and significantly decreased ejection fraction. Furthermore we detected reduced myocardial phosphocreatine to beta-ATP (PCr/b-ATP) ratios during the first week of acute disease. After 1 week we observed an improvement of PCr/b-ATP ratios by 68% and 34%, which was associated with an increase in left ventricular function. Our data suggest that 31P MRS might be a valuable tool in the evaluation of apical ballooning, but larger cohorts are needed to improve the understanding of metabolic changes during transient apical ballooning.

Aged↗

PubMed2006

Atrial and ventricular myocardium extraction using model-based techniques.

OBJECTIVES: This paper presents an efficient approach for extracting myocardial structures from given atrial and ventricular blood masses to enable non-invasive estimation of electrical excitation in human atria and ventricles. METHODS: Based on given segmented atrial and ventricular blood masses, the approach constructs the myocardial structure directly, in the case that the myocardium can be detected in the volume data, or by using mean model information, in the case that the myocardium cannot be seen in the volume data due to image modalities or artefacts. The approach employs mathematical and gray-value morphology operations. Regulated by the spatial visibility of the myocardial structure in the medical image data especially the atrial myocardium needs to be estimated repeatedly using the a-priori knowledge given by the anatomy. RESULTS: The approach was tested using eight patient data sets. The reconstruction process yielded satisfying results with respect to an efficient generation of a volume conductor model which is essential when trying to implement the estimation of electrical excitation in clinical application. CONCLUSION: The approach yields ventricular and atrial models that qualify for cardiac source imaging in a clinical setting.

Algorithms↗

PubMed2005

A signal processing pipeline for noninvasive imaging of ventricular preexcitation.

OBJECTIVES: Noninvasive imaging of the cardiac activation sequence in humans could guide interventional curative treatment of cardiac arrhythmias by catheter ablation. Highly automated signal processing tools are desirable for clinical acceptance. The developed signal processing pipeline reduces user interactions to a minimum, which eases the operation by the staff in the catheter laboratory and increases the reproducibility of the results. METHODS: A previously described R-peak detector was modified for automatic detection of all possible targets (beats) using the information of all leads in the ECG map. A direct method was applied for signal classification. The algorithm was tuned for distinguishing beats with an adenosine induced AV-nodal block from baseline morphology in Wolff-Parkinson-White (WPW) patients. Furthermore, an automatic identification of the QRS-interval borders was implemented. RESULTS: The software was tested with data from eight patients having overt ventricular preexcitation. The R-peak detector captured all QRS-complexes with no false positive detection. The automatic classification was verified by demonstrating adenosine-induced prolongation of ventricular activation with statistical significance (p <0.001) in all patients. This also demonstrates the performance of the automatic detection of QRS-interval borders. Furthermore, all ectopic or paced beats were automatically separated from sinus rhythm. Computed activation maps are shown for one patient localizing the accessory pathway with an accuracy of 1 cm. CONCLUSIONS: The implemented signal processing pipeline is a powerful tool for selecting target beats for noninvasive activation imaging in WPW patients. It robustly identifies and classifies beats. The small beat to beat variations in the automatic QRS-interval detection indicate accurate identification of the time window of interest.

Action Potentials↗

PubMed2005

Computationally efficient noninvasive cardiac activation time imaging.

OBJECTIVE: The computer model-based computation of the cardiac activation sequence in humans has been recently subject of successful clinical validation. This method is of potential interest for guiding ablation therapy of arrhythmogenic substrates. However, computation times of almost an hour are unattractive in a clinical setting. Thus, the objective is the development of a method which performs the computation in a few minutes run time. METHODS: The computationally most expensive part is the product of the lead field matrix with a matrix containing the source pattern on the cardiac surface. The particular biophysical properties of both matrices are used for speeding up this operation by more than an order of magnitude. A conjugate gradient optimizer was developed using C++ for computing the activation map. RESULTS: The software was tested on synthetic and clinical data. The increase in speed with respect to the previously used Fortran 77 implementation was a factor of 30 at a comparable quality of the results. As an additional finding the coupled regularization strategy, originally introduced for saving computation time, also reduced the sensitivity of the method to the choice of the regularization parameter. CONCLUSIONS: As it was shown for data from a WPWpatient the developed software can deliver diagnostically valuable information at a much shorter span of time than current clinical routine methods. Its main application could be the localization of focal arrhythmogenic substrates.

Arrhythmias, Cardiac↗

PubMed2003

Learning complex arithmetic--an fMRI study.

Aim of the present functional magnet resonance imaging (fMRI) study was to detect modifications of cerebral activation patterns related to learning arithmetic. Thirteen right-handed subjects were extensively trained on a set of 18 complex multiplication problems. In the following fMRI session, trained and untrained problems (closely matched for difficulty) were presented in blocked order alternating with a number matching task and a fact retrieval task. Importantly, left hemispheric activations were dominant in the two contrasts between untrained and trained condition, suggesting that learning processes in arithmetic are predominantly supported by the left hemisphere. Contrasting untrained versus trained condition, the left intraparietal sulcus showed significant activations, as well as the inferior parietal lobule. A further significant activation was found in the left inferior frontal gyrus. This activation may be accounted for by higher working memory demands in the untrained as compared to the trained condition. Contrasting trained versus untrained condition a significant focus of activation was found in the left angular gyrus. Following the triple-code model [Science 284 (1999) 970], the shift of activation within the parietal lobe from the intraparietal sulcus to the left angular gyrus suggests a modification from quantity-based processing to more automatic retrieval. The present study shows that the left angular gyrus is not only involved in arithmetic tasks requiring simple fact retrieval, but may show significant activations as a result of relatively short training of complex calculation.

Adult↗

PubMed2000

Magnetic resonance spectroscopy (MRS) in five patients with treated propionic acidemia.

Propionic acidemia is an inherited disorder caused by a defect of propionyl CoA carboxylase. Untreated, propionic acidemia leads to metabolic decompensation and toxic encephalopathy. We report on the magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) findings in five children who were properly treated by protein restriction and carnitine supplementation, during a phase of clinically and metabolically stable conditions. The examinations were performed on a whole-body 1.5 T scanner. During the observation period, from 1992 to 1996 we employed long echo time single-voxel spectroscopy and chemical shift imaging in addition to a conventional MRI protocol. The two children with the longest delay before onset of therapy showed cerebral atrophy. MRS yielded elevated lactate peaks in four of the children. These results indicate that MRS can detect metabolic alterations in the brains of children with propionic acidemia during metabolically stable conditions. The presence of lactate could be caused by hampered aerobic oxidation within the citrate cycle due to intracellular elevated propionic metabolites.

Amino Acid Metabolism, Inborn Errors↗

PubMed1996

Peripheral blood stem cell (PBSC) collection in extremely low-weight infants.

While PBSC collection has become a safe procedure for adults, only a few reports exist about its efficacy, safety and feasibility in paediatric patients, especially extremely low-weight infants. We describe successful PBSC collection in three infants of less than 10 kg body weight (BW; range: 6.92-9.4 kg) suffering from stage IV neuroblastoma. Harvest of PBSC started after mobilisation with high-dose chemotherapy and G-CSF, as soon as 1.0% CD34+ cells were detected. Collections were performed using a Baxter CS-3000 Plus separator primed with a mixture of irradiated, white cell-depleted and CMV-negative packed red cells resuspended in 5% human albumin and diluted with saline to match the patient's haematocrit. Performing a median of four, (4-7, median, range) procedures we collected at least 4 x 10(8)/kg BW nucleated cells (NC) from all three patients. The infants were not sedated and showed no serious side-effects. All three children were successfully transplanted with myeloid engraftment in 8 (7-9) days, independence from red cell support was achieved in 15 (10-20) days and from platelet transfusions in 25 (14-29) days after PBSC infusion. We conclude that PBSC harvesting using continuous flow cell separators is safe, even in low-weight infants of less than 7 kg BW.

Adrenal Gland Neoplasms↗