Piezoelectric power generation using heart motion

Cataloged from PDF version of article.The presence of pacemakers and implantable cardioverter-defibrillators (ICD) is considered historically a contraindication to magnetic resonance (MR) imaging. Main reason behind this contraindication is the current induced on the pacing leads during the MRI examination which may damage the cardiac tissues by heating or the pulse generator of the pacemaker with a reverse current. In this thesis an approach towards the solution of this problem is stated. It has been shown in previous work that replacing the pacing leads with fiber-optic cables minimizes the current induced on the leads. Drawback of this system is the increase in the power consumption of the pacemaker because of the fiber-optic cables and also necessity of an additional pulse generator circuitry near the heart. In this thesis, feasibility of using a piezoelectric power generator for compensating the increased power consumption is investigated. A novel piezoelectric geometry increasing the effective length in a given volume is designed. With this device the resonance frequency of the generator was decreased and the power output for a given volume is increased compared to standard rectangular piezoelectric bimorphs. When connected to a simple heart phantom the novel design produced 2.83 microwatts power whereas the standard rectangular bimorphs produced less than 1 microwatts. Although the output power is increased with the novel design, it was not sufficient to power a pulse generator circuitry that will be used to pace the heart.Afacan, OnurM.S

A normative spatiotemporal MRI atlas of the fetal brain for automatic segmentation and analysis of early brain growth.

Longitudinal characterization of early brain growth in-utero has been limited by a number of challenges in fetal imaging, the rapid change in size, shape and volume of the developing brain, and the consequent lack of suitable algorithms for fetal brain image analysis. There is a need for an improved digital brain atlas of the spatiotemporal maturation of the fetal brain extending over the key developmental periods. We have developed an algorithm for construction of an unbiased four-dimensional atlas of the developing fetal brain by integrating symmetric diffeomorphic deformable registration in space with kernel regression in age. We applied this new algorithm to construct a spatiotemporal atlas from MRI of 81 normal fetuses scanned between 19 and 39 weeks of gestation and labeled the structures of the developing brain. We evaluated the use of this atlas and additional individual fetal brain MRI atlases for completely automatic multi-atlas segmentation of fetal brain MRI. The atlas is available online as a reference for anatomy and for registration and segmentation, to aid in connectivity analysis, and for groupwise and longitudinal analysis of early brain growth

Moderators, Mediators, and Prognostic Indicators of Treatment With Hip Arthroscopy or Physical Therapy for Femoroacetabular Impingement Syndrome: Secondary Analyses From the Australian FASHIoN Trial.

BACKGROUND Although randomized controlled trials comparing hip arthroscopy with physical therapy for the treatment of femoroacetabular impingement (FAI) syndrome have emerged, no studies have investigated potential moderators or mediators of change in hip-related quality of life. PURPOSE To explore potential moderators, mediators, and prognostic indicators of the effect of hip arthroscopy and physical therapy on change in 33-item international Hip Outcome Tool (iHOT-33) score for FAI syndrome. STUDY DESIGN Cohort study; Level of evidence, 2. METHODS Overall, 99 participants were recruited from the clinics of orthopaedic surgeons and randomly allocated to treatment with hip arthroscopy or physical therapy. Change in iHOT-33 score from baseline to 12 months was the dependent outcome for analyses of moderators, mediators, and prognostic indicators. Variables investigated as potential moderators/prognostic indicators were demographic variables, symptom duration, alpha angle, lateral center-edge angle (LCEA), Hip Osteoarthritis MRI Scoring System (HOAMS) for selected magnetic resonance imaging (MRI) features, and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) score. Potential mediators investigated were change in chosen bony morphology measures, HOAMS, and dGEMRIC score from baseline to 12 months. For hip arthroscopy, intraoperative procedures performed (femoral ostectomy ± acetabular ostectomy ± labral repair ± ligamentum teres debridement) and quality of surgery graded by a blinded surgical review panel were investigated for potential association with iHOT-33 change. For physical therapy, fidelity to the physical therapy program was investigated for potential association with iHOT-33 change. RESULTS A total of 81 participants were included in the final moderator/prognostic indicator analysis and 85 participants in the final mediator analysis after exclusion of those with missing data. No significant moderators or mediators of change in iHOT-33 score from baseline to 12 months were identified. Patients with smaller baseline LCEA (β = -0.82; P = .034), access to private health care (β = 12.91; P = .013), and worse baseline iHOT-33 score (β = -0.48; P < .001) had greater iHOT-33 improvement from baseline to 12 months, irrespective of treatment allocation, and thus were prognostic indicators of treatment response. Unsatisfactory treatment fidelity was associated with worse treatment response (β = -24.27; P = .013) for physical therapy. The quality of surgery and procedures performed were not associated with iHOT-33 change for hip arthroscopy (P = .460-.665 and P = .096-.824, respectively). CONCLUSION No moderators or mediators of change in hip-related quality of life were identified for treatment of FAI syndrome with hip arthroscopy or physical therapy in these exploratory analyses. Patients who accessed the Australian private health care system, had smaller LCEAs, and had worse baseline iHOT-33 scores, experienced greater iHOT-33 improvement, irrespective of treatment allocation

Akışkan yataklı yakıcılarda nox emisyonlarının modellenmesi.

A comprehensive model, previously developed and tested for prediction of behavior of continuous fluidized bed combustors is extended to incorporate NOx formation and reduction reactions and applied to the simulation of METU 0.3 MWt Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) burning lignites with high volatile matter in their own ashes. The predictive accuracy of the model was assessed by comparing its predictions with measurements taken previously on the same rig. Favorable comparisons are obtained between the predicted and measured temperatures and concentrations of gaseous species along the combustor. Results show that determination of partitioning of coal nitrogen into char nitrogen and volatile nitrogen, and release of volatile nitrogen along the combustor are found to be the most important parameters that affect NOx formation and reduction in bubbling fluidized bed combustors. The system model proposed in this study proves to be a useful tool in qualitatively and quantitatively simulating the processes taking place in an atmospheric fluidized bed combustor.M.S. - Master of Scienc

Modeling of NOx emissions from fluidized bed combustion of high volatile lignites

A comprehensive model, previously developed and tested for prediction of behavior of continuous fluidized bed combustors is extended to incorporate NOx formation and reduction reactions and applied to the simulation of Middle East Technical University (METU) 0.3 MW Atmospheric Bubbling Fluidized Bed Combustor (ABFBC) burning lignites with high Volatile Matter/Fixed Carbon (VM/FC) ratios in their own ashes. Favorable comparisons are obtained between the predicted and measured temperatures and concentrations of gaseous species along the combustor. Results show that determination of partitioning of coal nitrogen into char-N and volatile-N, char combustion rate, and amount of volatile nitrogen released along the combustor are found to be the most important parameters that affect NO formation and reduction in bubbling fluidized bed combustors

Tissue microstructure information from T2 relaxometry and diffusion MRI can identify multiple sclerosis (MS) lesions undergoing blood-brain barrier breakdown (BBB)

International audienceGadolinium based contrast agents (GBCA) play a critical role in identifying MS lesions undergoing BBB which is of high clinical importance. However, repeated use of GBCAs over a long period of time and the risks associated with administering it to patients with renal complications has mandated for greater caution in its usage. In this work we explored the plausibility of identifying MS lesions undergoing BBB from tissue microstructure information obtained from T2 relaxometry and dMRI data. We also proposed a framework to predict MS lesions undergoing BBB using the tissue microstructure information and demonstrated its potential on a test case

Rapid measurement and correction of spatiotemporal B-0 field changes using FID navigators and a multi-channel reference image

Purpose To measure spatiotemporal B-0 field changes in real time using FID navigators (FIDnavs) and to demonstrate the efficacy of retrospectively correcting high-resolution T2*-weighted images using a novel FIDnav framework. Methods A forward model of the complex FIDnav signals was generated by simulating the effect of changes in the underlying B-0 inhomogeneity coefficients, with spatial encoding provided by a multi-channel reference image. Experiments were performed at 3T to assess the accuracy of B-0 field estimates from FIDnavs acquired from a 64-channel head coil under different shim settings and in 5 volunteers performing deep-breathing and nose-touching tasks designed to modulate the B-0 field. Second-order, in-plane spherical harmonic (SH) inhomogeneity coefficients estimated from FIDnavs were incorporated into an iterative reconstruction to retrospectively correct 2D gradient-echo images acquired in both axial and sagittal planes. Results Spatiotemporal B-0 field changes measured from rapidly acquired FIDnavs were in good agreement with the results of second-order SH fitting to the measured field maps. FIDnav field estimates accounted for a significant proportion of the Delta B-0 variance induced by deep breathing (64 +/- 21%) and nose touching (67 +/- 34%) across all volunteers. Ghosting, blurring, and intensity modulation artifacts in T2*-weighted images, induced by spatiotemporal field changes, were visibly reduced following retrospective correction with FIDnav inhomogeneity coefficients. Conclusions Spatially resolved B-0 inhomogeneity changes up to second order can be characterized in real time using the proposed approach. Retrospective FIDnav correction substantially improves T2*-weighted image quality in the presence of strong B-0 field modulations, with potential for real-time shimming