16,835 research outputs found
A method for delineation of bone surfaces in photoacoustic computed tomography of the finger
Photoacoustic imaging of interphalangeal peripheral joints is of interest in
the context of using the synovial membrane as a surrogate marker of rheumatoid
arthritis. Previous work has shown that ultrasound produced by absorption of
light at the epidermis reflects on the bone surfaces within the finger. When
the reflected signals are backprojected in the region of interest, artifacts
are produced, confounding interpretation of the images. In this work, we
present an approach where the photoacoustic signals known to originate from the
epidermis, are treated as virtual ultrasound transmitters, and a separate
reconstruction is performed as in ultrasound reflection imaging. This allows us
to identify the bone surfaces. Further, the identification of the joint space
is important as this provides a landmark to localize a region-of-interest in
seeking the inflamed synovial membrane. The ability to delineate bone surfaces
allows us not only to identify the artifacts, but also to identify the
interphalangeal joint space without recourse to new US hardware or a new
measurement. We test the approach on phantoms and on a healthy human finger
Chinese Expert Consensus on Critical Care Ultrasound Applications at COVID-19 Pandemic
The spread of new coronavirus (SARS-Cov-2) follows a different pattern than previous respiratory viruses, posing a serious public health risk worldwide. World Health Organization (WHO) named the disease as COVID-19 and declared it a pandemic. COVID-19 is characterized by highly contagious nature, rapid transmission, swift clinical course, profound worldwide impact, and high mortality among critically ill patients. Chest X-ray, computerized tomography (CT), and ultrasound are commonly used imaging modalities. Among them, ultrasound, due to its portability and non-invasiveness, can be easily moved to the bedside for examination at any time. In addition, with use of 4G or 5G networks, remote ultrasound consultation can also be performed, which allows ultrasound to be used in isolated medial areas. Besides, the contact surface of ultrasound probe with patients is small and easy to be disinfected. Therefore, ultrasound has gotten lots of positive feedbacks from the frontline healthcare workers, and it has played an indispensable role in the course of COVID-19 diagnosis and follow up
Sound radiation of 3 MHz driven gas bubbles
The sound radiation of 3 MHz acoustically driven air bubbles in liquid is
analysed with respect to possible applications in second harmonic ultrasound
diagnostics devices, which have recently come into clinical use. In the forcing
pressure amplitude P_a = 1-10 atm and ambient radius R_0 = 0.5-5 \mu m
parameter domain a narrow regime around the resonance radius R_0 \sim 1-1.5 \mu
m and relatively modest P_a \sim 2-2.5 atm is identified in which optimal sound
yield in the second harmonic is achieved while maintaining spherical stability
of the bubble. For smaller P_a and larger R_0 hardly any sound is radiated; for
larger P_a bubbles become unstable towards non-spherical shape oscillations of
their surface. The computation of these instabilities is essential for the
evaluation of the optimal parameter regime. A region of slightly smaller R_0
and P_a \sim 1-3 atm is best suited to achieve large ratios of the second
harmonic to the fundamental intensity. Spherical stability is guaranteed in the
suggested regimes for liquids with an enhanced viscosity compared to water,
such as blood.Comment: 19 pages, 10 low resolution ps-figures; higher resolution figures can
be retrieved from http://staff-www.uni-marburg.de/~hilgenfe/hires.htm
Radioactive Needlework, Reconstruction of needle-positions in radiation treatment
Nucletron presented a medical problem to the SWI 2006: how to find needles used for cancer treatment in a prostate? More concretely: how to find the positions of these needles from distorted images from an ultrasound probe? Section 1 explains the background of this problem. In Section 2 we deal with physical explanations for the distortions. In Section 3 we give a brief overview of medical imaging and explain which techniques we used to clean up the images
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