| 1. |
- Evertsson, Maria, et al.
(författare)
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Revolving permanent magnet causes rotating particle motion that makes new detection schemes possible in magnetomotive ultrasound
- 2019
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Ingår i: 2019 IEEE International Ultrasonics Symposium, IUS 2019. - 1948-5727 .- 1948-5719. - 9781728145976 - 9781728145969 ; 2019-October, s. 2373-2375
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Konferensbidrag (refereegranskat)abstract
- Magnetomotive ultrasound, MMUS, can reveal the presence of a magnetic contrast agent by applying an external magnetic field. If the interaction between the agent and the field is strong enough, a movement that can be detected by ultrasound is induced in the surrounding tissue, thereby inferring the contrast agent distribution. Electromagnets have been used to generate the necessary magnetic field, but due to their size, weight, and propensity to heat up, they are impractical to work with. Furthermore, the resulting magnetic force is directed mainly along the symmetry axis of such magnets, and thus the resulting movement is primarily a one-dimensional oscillation. We suggest the use of a rotating permanent magnet that generates a two-dimensional particle motion, and that this makes new detection schemes for MMUS possible. A prototype probe, containing a rotating neodymium magnet, was used to move a metallic sphere embedded in tissue-mimicking material. Cine loops recorded any in-plane movement with the magnetic probe placed in two different positions. A two-dimensional movement was demonstrated, using both our previously developed MMUS algorithm as well as a phase-based motion tracking algorithm. The conventional 1D MMUS processing detected the axial component in both magnetic probe positions, whereas the two-dimensional motion tracking algorithm estimated a rotational motion from the same measurements. The added dimension of motion could engender possibilities to more precise signal processing and thus improve robustness of magnetomotive motion detection. Moreover, the incorporation of a permanent magnet makes for a more practical device, as compared to using electromagnets.
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| 2. |
- Hill, David, et al.
(författare)
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Acousto-optic interaction strengths in optically scattering media using high pressure acoustic pulses
- 2021
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Ingår i: Biomedical Optics Express. - 2156-7085. ; 12:6, s. 3196-3213
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasound optical tomography (UOT) is a developing medical imaging technique with the potential to noninvasively image tissue oxygenation at depths of several centimeters in human tissue. To accurately model the UOT imaging, it is necessary the calculate the signal produced by the interaction between ultrasound and light in the scattering medium. In this paper we present a rigorous description for modeling this process for ultrasound pulses in the non-linear regime with peak pressures ranging up to the medical safety limit. Simulation results based on the presented model agree well with measurements performed with fully characterized ultrasound pulses. Our results also indicate that the UOT modeling process can be accurately simplified by disregarding the acoustically induced movement of scatterers. Our results suggest that the explored model and its software implementation can be used as a virtual lab to aid future development of pulses and UOT imaging algorithms.
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| 3. |
- Sheikh, Rafi, et al.
(författare)
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Clinical translation of a novel photoacoustic imaging system for examining the temporal artery
- 2019
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Ingår i: IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. - 0885-3010. ; 66:3, s. 472-480
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Tidskriftsartikel (refereegranskat)abstract
- The objective was to provide a clinical setup for photoacoustic imaging (PAI) of the temporal artery in humans and to describe the challenges encountered and methods of overcoming them. The temporal artery was examined in 7 patients with suspect giant cell arteritis (GCA), both in vivo and ex vivo, and the results were compared to that of histology. To adapt PAI to human studies, the transducer was fixed to an adjustable arm to reduce motion artifacts and a stepping motor was developed to enable 3D scanning. Risks associated with the use of lasers, ultrasound, and electrical equipment were evaluated by measuring energy levels, and safety precautions were undertaken to prevent injury to the patients and staff. The PAI spectra obtained clearly delineated the artery wall, both in vivo and ex vivo, although the latter were of higher quality due to the lack of artifacts. The results could be compared to that of histology. The energy levels involved were found to be below limits given in regulatory standards. Eye protectors prevented irradiation of the patient’s eyes, and visual function after the procedure was found not to be affected. The patients reported no discomfort during the investigations. PAI provides images of the temporal artery wall that may be used for the future diagnosis of GCA in humans. The technique could be further refined by addressing the specific problems of motion artefacts and interference from blood and other chromophores. This study paves the way for other clinical applications of PAI.
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