<p>Several groups have proposed classifying atherosclerotic disease by using acoustic radiation</p><p>force (ARF) elasticity methods to estimate the mechanical and material</p><p>properties of plaque. However, recent evidence suggests that cardiovascular disease</p><p>(CVD), in addition to involving pathological changes in arterial tissue, is also a</p><p>hemodynamic remodeling problem. As a result, integrating techniques that can</p><p>estimate localized hemodynamics relevant to CVD remodeling with existing ARF based</p><p>elastography methods may provide a more complete assessment of CVD.</p><p>This thesis describes novel imaging approaches for combining clinically-accepted,</p><p>ultrasound-based flow velocity estimation techniques (color-flow Doppler and spectral-</p><p>Doppler imaging) with ARF-based elasticity characterization of vascular tissue. Techniques</p><p>for integrating B-mode, color-flow Doppler, and ARFI imaging were developed</p><p>(BACD imaging), validated in tissue-mimicking phantoms, and demonstrated for in</p><p>vivo imaging. The resulting system allows for the real-time acquisition (< 20 Hz) of</p><p>spatially registered B-mode, flow-velocity, and ARFI displacement images of arterial</p><p>tissue throughout the cardiac cycle. ARFI and color-flow Doppler imaging quality,</p><p>transducer surface heating, and tissue heating were quantified for different frame-rate</p><p>and scan-duration configurations. The results suggest that BACD images can be acquired</p><p>at high frame rates with minimal loss of imaging quality for approximately</p><p>five seconds, while staying beneath suggested limits for tissue and transducer surface</p><p>heating.</p><p>Because plaque-burden is potentially a 3D problem, techniques were developed</p><p>to allow for the 3D acquisition of color-flow Doppler and ARFI displacement data</p><p>using a stage-controlled, freehand scanning approach. The results suggest that a</p><p>40mm x 20mm x 25mm BACD volume can be acquired in approximately three seconds.</p><p>Jitter, SNR, lesion CNR, soft-plaque detectability, and flow-area assessment were</p><p>quantified in tissue mimicking phantoms with a range of elastic moduli relevant</p><p>to ARFI imaging applications. Results suggest that both jitter and SNR degrade</p><p>with increased sweep velocity, and that degradation is worse when imaging stiffer</p><p>materials. The results also suggest that a transition between shearing-dominated</p><p>jitter and motion-dominated jitter occurs sooner with faster sweep speeds and in</p><p>stiffer materials. These artifacts can be reduced with simple, linear filters. Results</p><p>from plaque mimicking phantoms suggest that the estimation of soft-plaque area</p><p>and flow area, both important tasks for CVD imaging, are only minimally affected</p><p>at faster sweep velocities.</p><p>Current clinical assessment of CVD is guided by spectral Doppler velocity methods.</p><p>As a result, novel imaging approaches (SAD-SWEI, SAD-GATED) were developed</p><p>for combining spectral Doppler methods with existing ARF-based imaging</p><p>techniques to allow for the combined assessment of cross-luminal velocity profiles,</p><p>wall-shear rate (WSR), ARFI displacement and ARF-induced wave velocities. These</p><p>techniques were validated in controlled phantom experiments, and show good agreement</p><p>between previously described ARF-techniques and theory. Initial in vivo feasibility</p><p>was then evaluated in five human volunteers. Results show that a cyclic</p><p>variability in both ARFI displacement and ARF-generated wave velocity occurs during</p><p>the cardiac cycle. Estimates of WSR and peak velocity show good agreement</p><p>with previous ultrasonic-based assessments of these metrics. In vivo ARFI and Bmode/</p><p>WSR images of the carotid vasculature were successfully formed using ECG gating</p><p>techniques.</p><p>This thesis demonstrates the potential of these methods for the combined assessment</p><p>of vascular hemodynamics and elasticity. However, continued investigation</p><p>into optimizing sequences to reduce transducer surface heating, removing the angle</p><p>dependency of the SAD-SWEI/SAD-GATED methods, and decreasing processing</p><p>time will help improve the clinical viability of the proposed imaging techniques.</p> / Dissertation

名古屋大学博士学位論文 学位の種類 : 博士(医学)(論文) 学位授与年月日:平成5年9月14日 家田信人氏の博士論文として提出された

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 161-175).

Individuals with spinal cord injury (SCI) demonstrate reduced limb blood flow and muscle spasticity. It is plausible that the accumulation of metabolites, resulting from reduced perfusion, could exacerbate spasticity via activation of fusimotor neurons by Group III and IV afferents. PURPOSE: To determine the association between peripheral blood flow and muscle spasticity in persons with SCI. METHODS: A total of 16 individuals with SCI were classified into high (N=6), low (N=5), and no (N=5) spasticity groups according to their spasticity levels indicated by the modified Ashworth scale scores. Blood flow was measured in femoral and brachial arteries using duplex Doppler ultrasound and was normalized to limb lean mass obtained with dual energy X-ray absorptiometry. RESULTS: There were no significant group differences in age (30.5±4.15, 38.48±4.61, 32.6±4.89 years), time post SCI (8.5±4.2, 12.6±4.74, 6.8±1.66 years), American SCI Association motor scores (39.2±7.78, 59±12.34, 53.4±1.08), or sensory scores (96±22.1, 144.4±13.97, 130±13.8). Femoral artery blood flow, adjusted for limb lean mass, was significantly different (p=0.002) across the three leg spasticity groups (high 76.03±6.44, low 95.12±15.49, no 142.53±10.86 ml/min/kg).Total leg muscle spasticity scores were significantly and negatively correlated with femoral artery blood flow (r=-0.60, p=0.014). There was no significant difference in brachial artery blood flow between the three groups, indicating that the reduction in blood flow was confined to injured limbs and not due to systemic cardiovascular disorder. CONCLUSION: Among SCI patients, whole-leg blood flow is progressively lower in individuals with greater spasticity scores. These results suggest that a reduction in lower limb perfusion, among other factors, plays a significant role in the pathogenesis leading to muscle spasticity after SCI. / text

published_or_final_version / Surgery / Master / Master of Surgery

published_or_final_version / Medicine / Master / Master of Philosophy

Γενικά οι μη επεμβατικές τεχνικές παρουσιάζουν υψηλή ειδικότητα και ευαισθησία για τον καθορισμό του βαθμού της αρτηριακής στένωσης. Για τον λόγο αυτό οι μη επεμβατικές τεχνικές απεικόνισης είναι στην πρώτη γραμμή της διάγνωσης εμφραγμάτων κυκλοφορίας. Η μαγνητική αγγειογραφία (magnetic resonance angiography-MRA) έχει μια σημαντική θέση για την απεικόνιση αρτηριών και ιδιαίτερα των καρωτιδικών ανάμεσα στις μη επεμβατικές μεθόδους λόγω και της μη ιοντίζουσας ακτινοβολίας. Το βασικό πλεονέκτημα της MRA είναι η δυνατότητα απεικόνισης αιμοφόρων αγγείων σε μορφή ανάλογη με την ψηφιακή αγγειογραφία (digital subtraction angiography-DSA). Μπορούν να παραχθούν πολλαπλές προβολές των αρτηριών με τεχνικές μετά-επεξεργασίας, προσφέροντας μάλιστα περισσότερες πληροφορίες σχετικά με χαρακτηριστικά της ροή στην στένωση πέρα της εκτίμησης του ποσοστού της. Δημιουργούνται όμως ερωτήματα στο κατά πόσο η έμμεση εκτίμησης του ποσοστού μέσω της μείωσης της μέγιστης ταχύτητας ροής του ρευστού, είναι αξιόπιστη μέθοδος λαμβάνοντας υπόψη τα φαινόμενα στα οποία υπόκεινται οι πυρήνες, όντας φορείς της πληροφορίας και εκπομποί του σήματος, όπως η τυρβώδη ροή και τα φαινόμενα jet. / --

Reflexology is one of the top six complementary therapies used in the UK. Reflexologists claim that massage to specific points of the feet increases blood supply to referred or 'mapped' organs in the body. Empirical evidence to validate this claim is scarce. This three-phase RCT measured changes in haemodynamic parameters in subjects receiving reflexology treatment applied to specific areas of the foot which are thought to correspond to the heart (intervention) compared with reflexology applied to other areas on the foot which are not (control).

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