First principle simulation package for arbitrary acousto-optic interaction in scattering materials

We present and validate a simulation package for simulating the signal generated from arbitrary acousto-optical interaction in scattering media. We further present an example on how the package can be used as a virtual lab

Hemoglobin induces inflammation after preterm intraventricular hemorrhage by methemoglobin formation.

Cerebral intraventricular hemorrhage (IVH) is a major cause of severe neurodevelopmental impairment in preterm infants. To date, no therapy is available that prevents infants from developing serious neurological disability following IVH. Thus, to develop treatment strategies for IVH, it is essential to characterize the initial sequence of molecular events that leads to brain damage. In this study, we investigated extracellular hemoglobin (Hb) as a causal initiator of inflammation in preterm IVH

Characterization and modeling of acousto-optic signal strengths in highly scattering media

Ultrasound optical tomography (UOT) is an imaging technique based on the acousto-optic effect that can perform optical imaging with ultrasound resolution inside turbid media, and is thus interesting for biomedical applications, e.g. for assessing tissue blood oxygenation. In this paper, we present near background free measurements of UOT signal strengths using slow light filter signal detection. We carefully analyze each part of our experimental setup and match measured signal strengths with calculations based on diffusion theory. This agreement between experiment and theory allows us to assert the deep tissue imaging potential of ∼5 cm for UOT of real human tissues predicted by previous theoretical studies [Biomed. Opt. Express 8, 4523 (2017)] with greater confidence, and indicate that future theoretical analysis of optimized UOT systems can be expected to be reliable

Ultrasonic Methods for 2D Arterial Wall Movement Measurements

Cardiovascular diseases constitute the major cause of morbidity and mortality in the Western World. To increase our knowledge of cardiovascular diseases, it is important to find methods, preferably non-invasive ones, to study very early manifestations of vascular disease. Changes in the mechanical properties of the arteries can be an early manifestation of vascular disease. Further, changes in the mechanical properties of arteries can have important haemodynamic consequences, and are being increasingly recognised as important factors in cardiovascular morbidity and mortality. To obtain a measure of the mechanical properties in the arteries, arterial characterisation is performed. This thesis consists of seven papers concerning arterial characterisation and new ultrasonic methods for arterial characterisation. The first paper is an introduction and an overview of the area around vessel characterisation. Papers II and III describe and evaluate a new method for local non-invasive pulse-wave velocity (PWV) estimation. The PWV estimation was based on arterial-wall movement, which was detected by Tissue Doppler Imaging (TDI). The method was evaluated and optimised on an in vitro set-up and validated in vivo with respect to repeatability and reproducibility in a clinical study. In the evaluation, it was shown that system parameters have a significant effect on the PWV variance, whereas the PWV mean remains unchanged. Furthermore, it was established that high temporal resolution is the most vital parameter for minimising the PWV variance. The longitudinal movement of blood-vessel walls has so far gained little or no attention, as it has been presumed that these movements are of a negligible magnitude. The fourth paper presents results from the first in vivo study with a new unique ultrasonic method for measurement of both the radial and the longitudinal movement of the arterial wall, and it is shown that the magnitude of the longitudinal movement is not negligible, that movement due to breathing affects the recording of arterial longitudinal movement in common carotid artery, and that there was a shear stress present within the arterial wall in one volunteer. The new unique ultrasonic method is evaluated in vitro in paper V, and accuracy, reproducibility, and resolution were all considerably better than the resolution of the applied ultrasound scanner. The sixth paper describes a new method for arterial luminal diameter measurement with ultrasound. Features of the new method are its robustness, fastness, and resolution. The method was calibrated on a vessel phantom and was evaluated in vivo with respect to accuracy and reproducibility, which both were considerably better than the resolution of the applied ultrasound scanner. The seventh paper presents results from an in vivo study where a new digitised ultrasonic method called Elastart, which measures arterial lumen diameter at diastole and arterial distension with tissue Doppler, is compared with a golden standard method. The evaluation of the method in vivo against a golden standard showed that no difference in reproducibility between the two systems could be found. However, measurements of the arterial lumen diameter showed a slight underestimation of the Elastart system compared with the golden standard

Intra-Observer Variability of Longitudinal Movement and Intramural Shear Strain Measurements of the Arterial Wall using Ultrasound Non-Invasively in vivo

Using a recently developed high-resolution noninvasive ultrasonic method, we recently demonstrated that the intima-media complex of the common carotid artery show a bidirectional multiphasic longitudinal displacement of the same magnitude as the diameter change during the cardiac cycle. The longitudinal movement of the adventitial region was smaller, thus, we identified shear strain and, thus, shear stress, within the arterial wall. The aim of this study was to evaluate the intra-observer variability of measurement of the longitudinal displacement of the intima-media complex and the intramural shear strain of the common carotid artery in vivo using the new ultrasonic method. The evaluation was carried out by comparing two consecutive measurements on the common carotid artery of 20 healthy human subjects. According to the method of Bland Altman, we show that the systematic and random differences for the different phases of movement are acceptable in comparison to the measured displacement and no significant differences between the two measurements could be detected (p > 0.05 for all measured parameters). The coefficient of variation (CV) for measurement of the different phases of movement was ≤16%, including short-term physiologic variations. The higher variability in the measurement of the intramural shear strain (CV = 24%) has several explanations, which are discussed. In conclusion, this study shows that the present first ultrasonic method for high-resolution measurement of the longitudinal movement of the arterial wall is reliable and satisfactory for the further research of the longitudinal movement of the arterial wall in vivo. Further studies on the longitudinal movement of the arterial wall are important for developing an improved understanding of the physiology and the pathophysiology of the cardiovascular system

Individuell betygsättning av grupparbeten inom högre utbildning

Det finns många fördelar med att låta studenter vid högre utbildning gruppvis genomföra projektarbete med öppna frågeställningar. Det finns emellertid problem med att sätta individuella betyg i en kurs som till stor del examineras genom det gruppvisa projektarbetet. I kursen EEMA01 Medicinteknisk design ges valet av undervisningsform naturligt av lärandemålens karaktär men betygssättningen böravspegla individens bidrag i grupprocessen. Efter kritik från missnöjda studenter har lärarlaget i kursen nu utarbetat ett förslag till komplettering för att påverka betygsättning som uppfattats som orättvis

Initial Phantom Validation of Minute Roughness Measurement Using Phase Tracking for Arterial Wall Diagnosis Non-Invasively In Vivo

To detect minute roughness, we utilized the phase change that occurs in a radio frequency echo from the rough surface of an object during its lateral motion. The new method was optimized and validated using saw-tooth-shaped silicone phantoms sized from 13 to 33 mu m; results were compared to those obtained using a confocal laser scanning microscope

High-frequency ultrasound in the evaluation of cerebral intraventricular haemorrhage in preterm rabbit pups.

Cerebral intraventricular haemorrhage (IVH) is the most common cause of severe neurologic impairment following preterm birth in human infants. Ideally, an animal model for cerebral IVH should allow for reliable noninvasive evaluation of haemorrhagic extension and of subsequent development of posthaemorrhagic ventricular dilatation (PHVD). The aim of this study was to evaluate the use of high-frequency ultrasound (HFU) in premature rabbit pups with cerebral IVH induced by IP glycerol injection. Serial examinations using HFU enabled an accurate description of haemorrhagic extension and measurement of progressive PHVD over 72 h. The coefficient of variation for inter- and intraobserver variability in two measurements of ventricular size was less than 8.8% and 9.3%, respectively. Repeated ultrasound-guided intraventricular injection and sampling could be performed in vivo excluding requirement of stereotactic procedures and sedation. Application of HFU is a powerful tool for the evaluation of mechanisms involved in cerebral IVH and PHVD in the preterm rabbit pup model