Optoacoustic molecular Imaging

Die optoakustische molekulare Bildgebung bietet die Möglichkeit biologische Markermoleküle in-vivo mit hoher Empfindlichkeit zu lokalisieren. Um die Optoakustik im Hinblick auf ihren präklinischen und klinischen Einsatz weiterzuentwickeln, wurden in der vorliegenden Arbeit Methoden zur Optimierung der Sensitivität und der Spezifizität untersucht. Zu diesem Zweck wurde ein Simulationsprogramm für die Vorhersage von Frequenzen optoakustischer Signale entwickelt, um Daten mit optimalem Signal-Rausch-Verhältnis (SRV) durch den Einsatz von spektral abgestimmten Wandlern aufnehmen zu können. Darüber hinaus konnten das SRV und die Auflösung von optoakustischen Bildern durch die Entwicklung von angepassten Beamforming-Algorithmen signifikant verbessert werden. Im Rahmen der Untersuchungen zur Spezifizität wurden verschiedene Nanopartikel synthetisiert und in Bezug auf ihr Kontrastpotenzial verglichen. Des Weiteren wurden Methoden zur Kopplung von biologischen Liganden evaluiert und an einem Modellsystem aus Gold-Nanoshells und dem Antikörper Trastuzumab validiert. In ersten in-vivo Versuchen wurde schließlich die Machbarkeit der optoakustischen Darstellung von subkutanen Blutgefäßen in Echtzeit gezeigt. Ein Nachweisexperiment zur Machbarkeit der molekularen optoakustischen Bildgebung, bei dem die spezifische Kontrasterhöhung in arthritischen Kniegelenken durch die Injektion von antikörpermarkierten Goldnanorods gezeigt wurde, konnte ebenfalls erfolgreich in-vivo am Mausmodell durchgeführt werden.Optoacoustic molecular imaging can provide spatially resolved information about the presence of molecular markers in-vivo with high sensitivity. For further development of optoacoustic imaging towards a preclinical and clinical use, different methods for the enhancement of its sensitivity and specificity were investigated in this thesis. A simulation tool for the prediction of the frequency of optoacoustic signals was developed in order to be able to use spectrally matched transducers allowing data acquisition with optimized signal-to-noise ratio (SNR). Further, newly developed reconstruction and filter algorithms could enhance the SNR and the resolution of optoacoustic images significantly. Beyond that, different nanoparticle types were synthesized and compared with respect to their suitability as contrast agents. The synthesis was further optimized in terms of the particle's near-infrared absorption properties. In addition, different methods for binding biological targeting agents were developed and verified using a model system based on gold nanoshells and the monoclonal antibody Trastuzumab. First in-vivo trials for realtime optoacoustic imaging of subcutaneous blood vessels were performed successfully. Furthermore, a proof-of-concept experiment for validation of optoacoustic molecular imaging in which a specific contrast enhancement in arthritic mouse knee joints could be shown after intravenous injection of antibody modified gold nanorods was conducted

Blessures professionnelles et détresse psychologique chez les travailleurs immigrants au Canada : une analyse longitudinale de l’Enquête nationale sur la santé de la population

Le but de ce mémoire est d’étudier l’influence du statut d’immigrant sur la relation entre l’environnement immédiat de travail tel que défini par Karasek et Theorell (1990) d’une part, et la survenue de blessures professionnelles accidentelles (BPA) et la détresse psychologique d’autre part. Nos échantillons (N = 6 448 pour les analyses sur les BPA; N = 5 431 pour celles sur la détresse psychologique) proviennent de données longitudinales des neuf cycles de l’Enquête nationale sur la santé de la population (ENSP) de Statistique Canada (1994-2011) portant à la fois sur des travailleurs immigrants au Canada et sur des travailleurs natifs du Canada. Des analyses multiniveaux longitudinales ne permettent pas de confirmer un effet modérateur du statut d’immigrant pour les BPA ni pour la détresse psychologique. Toutefois, elles indiquent que les travailleurs immigrants sont significativement moins à risque de subir des BPA que les travailleurs natifs, un résultat à contre-courant des tendances décrites dans la plupart des recherches sur le sujet dans plusieurs pays industrialisés, à l’exception notable du Canada. La différence résiderait dans le profil sociodémographique des travailleurs immigrants au Canada qui ont un niveau d’éducation particulièrement élevé, mais rappelle aussi l’importance de considérer la sous-déclaration des BPA chez les travailleurs immigrants, particulièrement en contexte de données auto-rapportées. La probabilité de rapporter dans le temps de la détresse psychologique n’est pas significativement différente pour les travailleurs immigrants par rapport aux travailleurs natifs, mais ce résultat évoque quant à lui l’importance de considérer les différences culturelles dans la perception et l’évaluation de la détresse psychologique. Le fait d’être un travailleur appartenant à une minorité visible augmenterait considérablement les risques d’éprouver de la détresse psychologique, un résultat toutefois complètement médiatisé dès la prise en compte de caractéristiques de l’environnement immédiat de travail. Cette recherche se penche aussi sur les facteurs de l’environnement immédiat de travail (risques psychosociaux, contrat de travail) qui ont une influence sur la probabilité de subir une BPA ou de ressentir de la détresse psychologique dans le temps. Aucun des facteurs étudiés n’a d’impact à la fois sur la survenue des BPA et de la détresse psychologique, ce qui appuie la thèse que l’environnement immédiat de travail s’associe distinctement aux atteintes à la santé physique et mentale chez les travailleurs.The goal of this thesis is to study the impact of the immigrant status on the relationship between immediate work environment as defined by Karasek & Theorell (1990) on one hand, and the onset of accidental occupational injuries and psychological distress on the other hand. Our samples include both immigrant workers in Canada and Canadian-born workers (N = 6,448 for analyses on accidental occupational injuries; N = 5,431 for those on psychological distress) come from longitudinal data of all nine cycles of Statistics Canada’s National Population Health Survey (1994-2011). Multilevel longitudinal analyses do not make it possible to confirm the moderator effect of the immigrant status on accidental occupational injuries nor on psychological distress over time. However, they show that immigrant workers are less likely to suffer an accidental occupational injury. This result is out of step with most patterns described in research emanating from industrialized countries, with the notable exception of Canada. This could be explained by the sociodemographic profile of immigrants to Canada, who tend to have a particularly high level of education. This result also stresses the importance to consider the under-reporting of occupational injuries by immigrant workers, especially when studying self-reported data. Likeliness of declaring psychological distress over time is not significantly different for immigrant or Canadian-born workers, but this result raises the importance of taking into account cultural differences in perception and evaluation of psychological distress. Being a visible minority worker greatly increases the likeliness of suffer psychological distress, but this result is completely mediatized when considering immediate work environment characteristics. This research also focuses on the factors of immediate work environment (psychosocial risks, work contract) that influence the likeliness to suffer from an accidental occupational injury or psychological distress over time. None of the factors studied impinges both accidental occupational injury and psychological distress, which supports the thesis that immediate work environment is distinctly associated to damage to workers’ physic and psychological health

Application of Photoacoustic Methods and Confocal Microscopy for Monitoring of Therapeutic Response in Plaque Psoriasis

Psoriasis is prone to relapses and requires long-term therapy that may induce a range of adverse effects; therefore, an efficient and early detection of relapses is desirable. In this study, photoacoustic imaging and confocal laser scanning microscopic (CLSM) methods were investigated for their suitability in psoriasis follow-up examinations. Using a high-resolution photoacoustic system, the vascular structures of 11 psoriatic patients and 6 healthy volunteers were investigated. No differences were detected with respect to the average vessel diameter and vasculature per unit volume in the tissue of healthy volunteers and non-lesional and lesional skin areas of psoriatic patients. By means of CLSM, the diameters of the dermal papillae of 6 volunteers and 6 psoriatic patients were determined. The diameters of the dermal papillae of the healthy volunteers (0.074 +/- 0.006 mm) revealed no significant difference when compared to non-lesional skin areas of psoriatic patients (0.079 +/- 0.005 mm). The results obtained for the lesions in psoriatic patients showed a significant difference (Wilcoxon test, p = 0.028) between the diameters of the dermal papillae of the lesional skin areas 0.114 +/- 0.012 mm) and the non-lesional skin areas (0.079 +/- 0.005 mm). Thus, CLSM can be applied for monitoring psoriasis follow-up examinations

Needs and Attitudes of Older Chronic Back Pain Patients towards a Wearable for Ultrasound Biofeedback during Stabilization Exercises: A Qualitative Analysis

Chronic back pain has a high prevalence, especially in older adults, and seriously affects sufferers' quality of life. Segmental stabilization exercise (SSE) is often used during physiotherapy to enhance core stability. The execution of SSE requires the selective contraction of deep abdominal and back muscles. Motor learning can be supported using ultrasound imaging as visual biofeedback. ULTRAWEAR is a mobile ultrasound system that provides deep learning-based biofeedback on SSE execution, which is currently under development. We interviewed 15 older chronic back pain patients (CBPPs) to investigate their pain management behavior, experience with SSE, as well as their needs and requirements for ULTRAWEAR. We also gathered information about future-usage scenarios. CBPPs reported a high willingness to use the system as a feedback tool both in physiotherapeutic practices and at home. The automated detection and evaluation of muscle contraction states was highlighted as a major benefit of the system compared to the more subjective feedback provided by traditional methods such as palpation. The system to be developed was perceived as a helpful solution to support learning about SSE

Focused Ultrasound Treatment of a Spheroid In Vitro Tumour Model

SIMPLE SUMMARY: Ultrasound waves can be applied for diagnostic and therapeutic purposes. Focused ultrasound is approved for tissue ablation, e.g., in the treatment of uterine fibroids or essential tremors. Besides the non-invasive image-guided surgical intervention at temperatures above 55 °C, FUS is investigated in other fields like blood-brain barrier opening, hyperthermia, and neuromodulation. FUS offers potential as an adjuvant therapy in cancer treatment. Therefore, analysis of FUS effects on cancer cells is necessary. We performed studies on two human cancer cell line spheroids using a newly developed high-throughput in vitro FUS applicator with 32 individual transducers. This study aimed to perform basic experiments with a new in vitro FUS device on a 3D tumour model to acquire insight into the effects of FUS at the cellular level. These experiments may contribute to a better understanding and predictions of cancer treatment efficacy. ABSTRACT: Focused ultrasound (FUS) is a non-invasive technique producing a variety of biological effects by either thermal or mechanical mechanisms of ultrasound interaction with the targeted tissue. FUS could bring benefits, e.g., tumour sensitisation, immune stimulation, and targeted drug delivery, but investigation of FUS effects at the cellular level is still missing. New techniques are commonly tested in vitro on two-dimensional (2D) monolayer cancer cell culture models. The 3D tumour model—spheroid—is mainly utilised to mimic solid tumours from an architectural standpoint. It is a promising method to simulate the characteristics of tumours in vitro and their various responses to therapeutic alternatives. This study aimed to evaluate the effects of FUS on human prostate and glioblastoma cancer tumour spheroids in vitro. The experimental follow-up enclosed the measurements of spheroid integrity and growth kinetics, DNA damage, and cellular metabolic activity by measuring intracellular ATP content in the spheroids. Our results showed that pulsed FUS treatment induced molecular effects in 3D tumour models. With the disruption of the spheroid integrity, we observed an increase in DNA double-strand breaks, leading to damage in the cancer cells depending on the cancer cell type

Evaluation of a developed MRI-guided focused ultrasound system in 7 T small animal MRI and proof-of-concept in a prostate cancer xenograft model to improve radiation therapy

Focused ultrasound (FUS) can be used to physiologically change or destroy tissue in a non-invasive way. A few commercial systems have clinical approval for the thermal ablation of solid tumors for the treatment of neurological diseases and palliative pain management of bone metastases. However, the thermal effects of FUS are known to lead to various biological effects, such as inhibition of repair of DNA damage, reduction in tumor hypoxia, and induction of apoptosis. Here, we studied radiosensitization as a combination therapy of FUS and RT in a xenograft mouse model using newly developed MRI-compatible FUS equipment. Xenograft tumor-bearing mice were produced by subcutaneous injection of the human prostate cancer cell line PC-3. Animals were treated with FUS in 7 T MRI at 4.8 W/cm2 to reach ~45 °C and held for 30 min. The temperature was controlled via fiber optics and proton resonance frequency shift (PRF) MR thermometry in parallel. In the combination group, animals were treated with FUS followed by X-ray at a single dose of 10 Gy. The effects of FUS and RT were assessed via hematoxylin-eosin (H&E) staining. Tumor proliferation was detected by the immunohistochemistry of Ki67 and apoptosis was measured by a TUNEL assay. At 40 days follow-up, the impact of RT on cancer cells was significantly improved by FUS as demonstrated by a reduction in cell nucleoli from 189 to 237 compared to RT alone. Inhibition of tumor growth by 4.6 times was observed in vivo in the FUS + RT group (85.3%) in contrast to the tumor volume of 393% in the untreated control. Our results demonstrated the feasibility of combined MRI-guided FUS and RT for the treatment of prostate cancer in a xenograft mouse model and may provide a chance for less invasive cancer therapy through radiosensitization

Wave front analysis for enhanced time-domain beamforming of point-like targets in optoacoustic imaging using a linear array

Using linear array transducers in combination with state-of-the-art multichannel electronics allows to perform optoacoustic imaging with frame rates only limited by the laser pulse repetition frequency and the acoustic time of flight. However, characteristic image artefacts resulting from the limited view and a lower SNR when compared to systems based on single-element focused transducers represent a burden for the clinical acceptance of the technology. In this paper, we present a new method for the improvement of image quality based on the analysis of the signal amplitudes along summation curves during the delay-and-sum beamforming process (DAS). The algorithm compares amplitude distributions along wave fronts with theoretical patterns from optoacoustic point sources. The method was validated on simulated and experimental phantom as well as in-vivo data. An improvement of the lateral resolution by more than a factor of two when comparing conventional DAS and our approach could be shown (numeric and experimental phantom data). For instance, on experimental data from a wire phantom, a PSF in the range of 0.18–0.22 mm was obtained with our approach against 0.48 mm for standard DAS. Furthermore, the SNR of a subcutaneous vessel 2.5 mm below the skin surface was improved by about 30 dB when compared to standard DAS

Polymeric Entrapped Thiol-Coated Gold Nanorods: Cytotoxicity and Suitability as Molecular Optoacoustic Contrast Agent

The behaviour of polymeric entrapped thiol-coated GNRs in culture medium under biological conditions was analysed. The in vitro cytotoxicity was studied by a Colony Forming Efficiency assay on immortalized mouse fibroblasts (Balb/3T3) obtaining a dose-effect relationship in which an Inhibitory Concentration at 50% (IC50) was 20.3µM. The suitability of the new nanomaterial as optoacoustic contrast agent was investigated in phantom studies using a hardware platform suitable for retrieving clinically relevant data. Spherical alginate phantoms containing GNR-2-PNP at different concentrations were synthesized and the optoacoustic signal amplitudes were measured as a function of concentration. Signals could be obtained with satisfying SNR down to concentrations of 11 µM corresponding to subtoxic concentration in our in vitro model. The nanomaterial showed to be a suitable and promising contrast agent for different optoacoustic imaging modalities including multispectral approaches.JRC.I.4-Nanobioscience

Real-Time Volumetric Ultrasound Research Platform with 1024 Parallel Transmit and Receive Channels

Volumetric ultrasound imaging is of great importance in many medical fields, especially in cardiology, but also in therapy monitoring applications. For development of new imaging technologies and scanning strategies, it is crucial to be able to use a hardware platform that is as free and flexible as possible and does not restrict the user in his research in any way. For this purpose, multi-channel ultrasound systems are particularly suitable, as they are able to control each individual element of a matrix array without the use of a multiplexer. We set out to develop a fully integrated, compact 1024-channel ultrasound system that provides full access to all transmission parameters and all digitized raw data of each transducer element. For this purpose, we synchronize four research scanners of our latest “DiPhAS” ultrasound research system generation, each with 256 parallel channels, all connected to a single PC on whose GPUs the entire signal processing is performed. All components of the system are housed in a compact, movable 19-inch rack. The system is designed as a general-purpose platform for research in volumetric imaging; however, the first-use case will be therapy monitoring by tracking radiation-sensitive ultrasound contrast agents