The propagation of ultrasound through two- and three-dimensional strongly scattering media, with either random or ordered internal structures, has been investigated through experiments and finite element simulations. All media investigated have strong scattering resonances, leading to novel transport behaviour. The two-dimensional samples consist of nylon rods immersed in water. When the nylon rods are arranged in a triangular lattice to form two-dimensional phononic crystals, very unusual dispersion properties are observed when the lattice constant is adjusted so that Bragg and hybridization gaps overlap in frequency. This behaviour is attributed to the competition between two co-existing propagating modes, leading to a new method for tuning bandgap properties and adjusting the transmission by orders of magnitude. The scattering resonance of the nylon rods also leads to unusual Dirac cone properties at the K point of the triangular lattice. The three-dimensional media were fabricated by brazing aluminum beads together to form a disordered porous solid network, with either vacuum or air in the pores, depending on the experiment. This system is of particular interest because it has been shown to exhibit Anderson localization of ultrasound. Two experimental approaches were developed to investigate previously unstudied properties of this system. By directly counting the modes in the frequency domain, the density of states was measured. At intermediate frequencies, the density of states was found to be approximately independent of frequency, while at higher frequencies, the frequency dependence was consistent with traditional density-of-states models. The level statistics of the modes was also investigated to determine the conditions under which level repulsion occurs. By using a laser interferometer to measure the ultrasonic displacements on the surface of a large slab-shaped sample, sub-diffusive behaviour was observed, demonstrating the feasibility of using such measurements to investigate the transition to Anderson localization in these samples.

The work presented in this thesis investigates novel modalities to guide Transcranial Magnetic Resonance guided Focused Ultrasound (TcMRgFUS). TcMRgFUS is an emerging and promising non-invasive technique for the treatment of neurological disorders, such as essential tremor or Parkinsonian tremor. A novel Magnetic Resonance Acoustic Radiation Force Imaging (MRARFI) has been used to image the location of the ultrasonic beam produced by a preclinical prototype: an accelerated 2D spin-echo MR ARFI pulse sequence has been introduced to generate undistorted ultrasound-induced displacement maps in ex vivo veal brains with minimum energy deposition. We then investigated direct effects of the ultrasonic beam on brain activity by conducting in vivo ultrasonic neuromodulation, similarly to what is currently achieved with transcranial magnetic stimulation (TMS) but with the millimetric targeting capabilities of the ultrasound. Experiments have been first conducted in an anesthetized rat model to investigate the motor threshold. Numerical simulations have shown that the acoustic pattern in the rat head is affected by reverberations and that special care must be taken when relating acoustic parameters to neurostimulation effects, especially at a low frequency and for small animals. Finally, for the first time, we used low intensity FUS stimulation to causally modulate behavior in an awake nonhuman primate brain. We showed that the latency of an anti-saccade task was delayed significantly in the presence of ultrasonic beam focused in the Frontal Eye Field. Sham experiments did not show any significant change in the latencies.

Introduction: No protocol for assessing ultrasound imaging skill has been validated. We sought to develop and validate an assessment protocol for ultrasound imaging for the Focused Assessment with Sonography for Trauma. Methods: Our assessment tool consisted of task checklists, a global rating scale, and hand-motion analysis and was developed by a modified Delphi technique. Novice and expert cohorts were recruited to perform a FAST exam on a volunteer for assessment under the protocol. Results: Experts scored higher on static image acquisition (11.58 of 16 versus 6.63, p<0.0001), dynamic image acquisition (17.21 of 24 versus 11.08, p=0.0005), and our global rating scale (29.79 of 40 versus 18.42, p<0.0001); experts used fewer movements (263.0 movements versus 452.4, p=0.0216) and a shorter path length than novices (60.097 m versus 32.777 m, p=0.0041). Conclusion: Our protocol for assessing ultrasound imaging skill has criterion validity in assessing expertise and may lead to improvements to training and credentialing programs.

Background: Transrectal ultrasound is commonly performed in the clinical evaluation of the prostate. Ultrasound-guided randomized sextant biopsy became the standard procedure for the diagnosis of carcinoma of the prostate (CaP). A guided biopsy of sonographically irregular lesions of the prostate is not performed in randomized biopsies. An almost generally accepted opinion is that hypoechoic lesions are suspicious for the presence of CaP. However, the role of prostatic lesions with an echogenicity other than iso- or hypoechoic, e.g. hyperechoic or irregular lesions in relation to CaP is not clear. The intention of the present prospective study was to clarify the role of different prostatic ultrasound findings with a new-generation ultrasound probe in regard to their relevance concerning the presence of cancer. Material and Methods: 265 patients who were referred for prostatic evaluation because of an elevated PSA serum level or a positive digital rectal examination were enrolled in a prospective study. All patients had a systematic ultrasound-guided sextant biopsy of the prostate and a 4-core biopsy of the transition zone. All biopsy cores taken were guided by transrectal ultrasound. In case of a sonographically suspicious lesion, biopsy was always directed into this area. The predominant ultrasound appearance was separately recorded for each core. Results: Carcinoma of the prostate was detected in 87 (32.8%) of the 265 patients. Biopsy cores with isoechoic ultrasound findings revealed CaP in 7.6%. The data for hypoechoic, hyperechoic, mixed-echoic and anechoic lesions were 34.5, 26.9, 21.1 and 0%, respectively. Hypoechoic ultrasound findings were less frequently found in the transition zone of the prostate, but the rate of CaP detection was the same as in the peripheral zone of the prostate. Conclusions:The transrectal ultrasound pattern of the prostate yields important information about the presence of carcinoma of the prostate. Especially hypoechoic lesions indicate the presence of CaP in a significant proportion of cases. However, hyperechoic lesions and lesions of mixed or irregular echogenicity were found to contain cancer in significant numbers as well, and should therefore be considered to be suspicious for cancer when performing transrectal ultrasound of the prostate. Directed biopsy of irregular ultrasound patterns in the prostate seems therefore to be recommendable. / Hintergrund: Der transrektale Ultraschall ist die häufigste bildgebende Untersuchung zur klinischen Beurteilung der Prostata. Zur Diagnostik des Prostatakarzinoms (PCa) hat sich die ultraschallgesteuerte Sextanten-Biopsie als Standardverfahren etabliert. Eine gezielte Biopsie irregulärer Ultraschallbezirke ist hier nicht vorgesehen. Es ist jedoch bekannt, daß sonographisch echoarm erscheinende Areale suspekt für die Präsenz eines PCa sind. Die Wertigkeit nicht einheitlicher oder echoreicher Ultraschallmuster ist jedoch bisher nicht zweifelsfrei geklärt. Ziel der vorliegenden Arbeit war es, mit einem Ultraschallgerät der neuesten Generation die Bedeutung der verschiedenen Ultraschallmuster bezüglich des Vorhandenseins von Prostatakarzinomen zu klären. Material und Methoden: 265 Patienten mit erhöhten PSA-Serumwerten oder suspekten Tastbefunden der Prostata wurden in die prospektive Untersuchung eingeschlossen. Bei allen Patienten wurden systematische, ultraschallgesteuerte Prostatabiopsien, wie in der Sextantenbiopsie vorgesehen, und 4 Zylinder aus der Transitionalzone entnommen. Bei der Biopsie wurde jedoch gezielt die Punktion in Bereichen von – falls vorhanden – irregulärem Ultraschallmuster vorgenommen und das entsprechende Ultraschallbild dokumentiert. Ergebnisse: Bei 87 der 265 Patienten (32,8%) wurden Prostatakarzinome nachgewiesen. Biopsiezylinder aus isodensen Bereichen wiesen in 7,6% ein Prostatakarzinom auf. Die Karzinomhäufigkeit bei Biopsie von echoarmen und echoreichen Arealen sowie von Arealen mit unterschiedlichen Echomustern und von zystischen Arealen wurde mit 34,5, 26,9, 21,1 bzw. 0% ermittelt. Echoarme Befunde wurden seltener in der Transitionalzone nachgewiesen, waren jedoch dort in etwa gleicher Häufigkeit mit einem Karzinom verbunden wie in der peripheren Zone. Schlußfolgerungen: Das transrektale Ultraschallmuster in der Prostata liefert wichtige Hinweise auf das Vorhandensein eines Prostatakarzinoms. Insbesondere echoarme Läsionen deuten auf ein PCa hin. Echoreiche Läsionen und solche mit unterschiedlichen Echomustern enthielten jedoch Karzinome in so bedeutender Anzahl, daß diese Läsionen ebenfalls als karzinomverdächtig eingestuft werden müssen und auch eine gezielte Biopsie dieser Areale im Rahmen der Sextantenbiopsie empfehlenswert erscheint. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

This thesis focuses on expectant parents’ experiences and needs when soft makers are detected at mid-trimester ultrasound, resulting in an unexpected assessment of risk for fetal anomalies. The thesis also describes the prevalence of ultrasonographic fetal soft markers and the incidence of Down syndrome in a low-risk population of 10,535 pregnant women with a total of 10,710 fetuses, as well as the risk of invasive prenatal diagnostics in conjunction with the detection of soft markers. Finally, the thesis aims to explore the value of a web-based patient decision aid (DA) in facilitating informed decision making regarding routine fetal screening for anomalies and the fathers’ role in decision making regarding prenatal screening. A prospective observational study was conducted between 2008–2011 to investigate the prevalence of ultrasonographic fetal soft markers at second trimester screening. During this time period, 12 women and 17 men were interviewed about their experience when soft markers were detected. Based on the results of these interviews, a web-based decision aid (DA) to enhance expectant parents’ decision-making concerning fetal screening was developed and a trial initiated to test its utility. Interviews were conducted with 17 women who received access to the DA, 11 who had chosen to use the DA and six who had not used it. All interview studies were analysed using systematic text condensation (STC) developed by Malterud. Soft markers were detected in 5.9% of the fetuses at mid-trimester ultrasound, whereof 5.1% were isolated. All soft markers showed a positive likelihood ratio (LR+) for DS; however, the association was only statistically significant for the collapsed category ‘any marker’ (isolated, multiple or combined with anomaly), not for isolated markers. An almost 24-fold increase of invasive diagnostic testing was shown in all women, including those with a low estimated risk for aneuploidy, i.e. &lt; 1/200 (paper III). The results from interviews showed that the finding of soft markers created much anxiety and indicated that both women and men lacked awareness of the potential of the ultrasound examination (papers I and II). The results also showed that the men were actively engaged in decision making not only by supporting their partners, but also considered their own values and needs regarding these issues (paper II). It was also evident that women wanted their partners to be engaged in decisions regarding fetal diagnostics (papers I and IV). The web-based patient DA was able to initiate a process of conscious decision making in pregnant women, as a result of their interaction with the tool. The DA allowed for clarification of women’s thoughts and priorities and helped them to understand the significance of the screening result and providing a basis for making informed decisions regarding fetal screening (paper IV).

I assessed the accuracy of two clinical prediction rules, the d-dimer blood test and point of care ultrasound for diagnosing lower limb deep vein thrombosis. Emergency physicians were trained in ultrasound and prospectively scanned emergency department patients with suspected deep vein thrombosis. Accuracy of the Wells and AMUSE rules and the ultrasound result was compared to radiology-performed ultrasound and a 90-day clinical outcome. Univariate and multivariate analyses were performed assessing which factors were associated with the outcome. The sensitivity and specificity of the Wells score for the clinical outcome was 85.7% and 68.5%; the AMUSE score 85.7% and 54.4%. Ultrasound had a sensitivity of 91.7% and specificity of 91.7% for radiology-diagnosed thrombus and 78.6% and 95.0% for clinical outcome. The odds ratio of a positive outcome with a positive ultrasound was 65.1. After receiving the ultrasound training program, emergency physicians were unable to demonstrate sufficient accuracy to replace current diagnostic strategies.

Šis magistro baigiamasis darbas yra apie arklių šlubavimus ir dažniausiai naudojamus klinikinės diagnostikos metodus juos diagnozuoti. Šiam tyrimui buvo pasirinkta Danijos Horsholm Hestepraksis klinika, tyrimas atliktas nuo Liepos 1d iki Spalio 1d. Ši klinika yra viena iš didžiausių specializuotų arklių veterinarijos klinikų Danijoje. Šis darbas susideda iš 4 skyrių, kurie susideda iš įvado, literatūros apžvalgos, rezultatų, rezultatų aptarimo ir išvadų. Darbe yra 34 puslapiai, su 2 lentelėmis ir 22 paveikslėliais. Šiam tyrimui pasirinkta šimtas atsitiktinų arklių, kuriem buvo diagnozuota galūnių ligos. Buvo analizuojama kaip šlubavimui įtakos turi lytis, amžius, arklio veislė. Buvo nustatyta, kad dažniausiai šlubavimo problemų turintys arkliai, gydyti Horsholm Hestepraksis, yra sportui naudojami arkliai. Todėl pagrindinės galūnių ligos yra susyjusios su sąnarių, sausgyslių ir raiščių problemomis. Pagrindinės pažeistos kojos yra priekinės kojos, ypač priekinė kairė koja. / The current work is about horse lameness and the most common and useful clinical diagnostic methods to find it. For this research the Horsholm Hestepraksis clinic in Denmark was chosen, the term from July 01 to October 01 in 2013. This clinic is one of Denmark's largest specialised veterinary clinics in the field of equine diseases. This work consists of 4 chapters which consist from introduction, literature review, results, discussion of the results and conclusion. There are 34 pages with 2 tables and 22 pictures. 100 random horses were choosen for this work, which had diagnosed limb lameness. It was analyzed what is most common sex, age, breed of the horses. It was analyseds that the most common horses, which are treated in Horsholm Hestepraksis, are horses used for sport activity. Therefore the main limb diseases are related to joint, tendon and ligaments damage. The most common legs are front legs, especially front left leg.

The primary objective of this thesis was to gain a deeper understanding of acoustic wave propagation in phononic crystals, particularly those that include materials whose properties can be varied periodically in time. This research was accomplished in three ways. First, a 2D phononic crystal was designed, created, and characterized. Its properties closely matched those determined through simulation. The crystal demonstrated band gaps, dispersion, and negative refraction. It served as a means of elucidating the practicalities of phononic crystal design and construction and as a physical verification of their more interesting properties. Next, the transmission matrix method for analyzing 1D phononic crystals was extended to include the effects of time-varying material parameters. The method was then used to provide a closed-form solution for the case of periodically time-varying material parameters. Some intriguing results from the use of the extended method include dramatically altered transmission properties and parametric amplification. New insights can be gained from the governing equations and have helped to identify the conditions that lead to parametric amplification in these structures. Finally, 2D multiple scattering theory was modified to analyze scatterers with time-varying material parameters. It is shown to be highly compatible with existing multiple scattering theories. It allows the total scattered field from a 2D time-varying phononic crystal to be determined. It was shown that time-varying material parameters significantly affect the phononic crystal transmission spectrum, and this was used to switch an incident monochromatic wave. Parametric amplification can occur under certain circumstances, and this effect was investigated using the closed-form solutions provided by the new 1D method. The complexity of the extended methods grows logarithmically as opposed linearly with existing methods, resulting in superior computational complexity for large numbers of scatterers. Also, since both extended methods provide analytic solutions, they may give further insights into the factors that govern the behaviour of time-varying phononic crystals. These extended methods may now be used to design an active phononic crystal that could demonstrate new or enhanced properties.

The primary objective of this thesis was to gain a deeper understanding of acoustic wave propagation in phononic crystals, particularly those that include materials whose properties can be varied periodically in time. This research was accomplished in three ways. First, a 2D phononic crystal was designed, created, and characterized. Its properties closely matched those determined through simulation. The crystal demonstrated band gaps, dispersion, and negative refraction. It served as a means of elucidating the practicalities of phononic crystal design and construction and as a physical verification of their more interesting properties. Next, the transmission matrix method for analyzing 1D phononic crystals was extended to include the effects of time-varying material parameters. The method was then used to provide a closed-form solution for the case of periodically time-varying material parameters. Some intriguing results from the use of the extended method include dramatically altered transmission properties and parametric amplification. New insights can be gained from the governing equations and have helped to identify the conditions that lead to parametric amplification in these structures. Finally, 2D multiple scattering theory was modified to analyze scatterers with time-varying material parameters. It is shown to be highly compatible with existing multiple scattering theories. It allows the total scattered field from a 2D time-varying phononic crystal to be determined. It was shown that time-varying material parameters significantly affect the phononic crystal transmission spectrum, and this was used to switch an incident monochromatic wave. Parametric amplification can occur under certain circumstances, and this effect was investigated using the closed-form solutions provided by the new 1D method. The complexity of the extended methods grows logarithmically as opposed linearly with existing methods, resulting in superior computational complexity for large numbers of scatterers. Also, since both extended methods provide analytic solutions, they may give further insights into the factors that govern the behaviour of time-varying phononic crystals. These extended methods may now be used to design an active phononic crystal that could demonstrate new or enhanced properties.

Microbubble contrast agents for ultrasound are widely used in numerous medical applications, both diagnostic and therapeutic. Due to their size, similar to that of red blood cells, microbubbles are able to traverse the entire vascular bed, enabling their utilization for applications such as tumour diagnosis. Vaporizable submicron droplets of liquid perfluoro- carbon potentially represent a new generation of extravascular contrast agents for ultrasound. Droplets of a few hundred nanometers in diameter have the ability to extravasate selectively in regions of tumour growth while staying intravascular in healthy tissues. Upon extravasation, these droplets may be vaporized with ultrasound and converted into gas bubbles. In this thesis we argue that vaporized submicron perfluorocarbon droplets possess the necessary stability and acoustic characteristics to be potentially applicable as a new gener- ation of extravascular ultrasound contrast agents. We examine, separately, the ultrasound conditions necessary for vaporization of the droplets into microbubbles, the size and stability of these bubbles following vaporization, on timescales ranging from nanoseconds to minutes, and the bubbles’ acoustic response to incident diagnostic ultrasound. We show that submicron droplets may be vaporized into bubbles of a few microns in diameter using single ultrasound pulse within the diagnostic range. The efficiency of conversion is shown to be on the order of at least 10% of the exposed droplets converting into stable microbubbles. The bubbles are shown to be stabilized by the original coating material encapsulating the droplet precursors, and be stable for at least minutes following vaporization. Finally, vaporized droplets are shown to be echogenic, with acoustic characteristics comparable to these of the commercially available ultrasound contrast agents. The results presented here show that vaporized droplets possess the necessary stability properties and echogenicity required for successful application as contrast agents, suggesting potential for their future translation into clinical practice.