Ultrasound-Computed Tomography (CT)

The experiment clearly shows how an ultrasound CT image is created. The relevance and differences of individual measurement parameters such as attenuation and speed of sound are analyzed and the influence of filters and image processing is investigated.

Keywords: reflection, scattering, transmission, absorption, sound attenuation, sound speed, resolution, ultrasound echography (A-image, B-image), tomography, CT image, image processing, filter

X-ray CT, MRI and PET are computer-aided imaging procedures that are used in medical diagnostics, industry and research. Processes such as radiation absorption, nuclear magnetic resonance or particle emission are used to generate cross-sectional images using correspondingly measurable physical quantities. Ultrasound computed tomography is another CT procedure. It differs from X-ray CT in that instead of the attenuation of X-rays, the attenuation and the travel times of ultrasound signals in the object being examined are measured. In our ultrasound CT, line scans are recorded at different angles and combined to form a cross-sectional image. The sample arranged between the transmitting and receiving probes is moved and rotated under computer control. The superimposition of the projections of individual scans can be followed step by step on the PC.

GS-EchoView software interface in CT mode

The experiment follows the process of generating an ultrasound computer tomogram (ultrasound measurement > projection > back projection > tomogram) step by step. Sound attenuation and sound velocity tomograms are recorded and analyzed for different settings of the transmission power and amplification.
The use of a filter algorithm to improve the image quality of CT images is discussed using the Shepp-Logan filter. By changing the parameters for scaling the color values ​​or gray values, simple image processing can be carried out in which the brightness, contrast and color of the CT images are changed.

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