Article No. VK-PHY09

PHY09 Ultrasonic computer tomography (CT)

Demonstration of the formation of an ultrasonic CT scan

In this experiment the formation of an ultrasonic CT scan image is clearly shown. The relevance and differences of individual measurement parameters such as attenuation and sound velocity are analysed and the influence of filters and image processing is investigated.

Keywords: Reflection, scattering, transmission, absorption, acoustic attenuation, sound velocity, resolution, ultrasonic echography (A-Scan, B-Scan), tomography, CT scan image, image processing, filters

X-ray CT, MRT and PET are computer-aided imaging methods used in medical diagnostics, industry and research. Processes such as radiation absorption, nuclear magnetic resonance or particle emission are used to produce cross-sectional images by means of appropriately measurable physical quantities. Ultrasonic computer tomography is another CT method. It differs from X-ray CT in that instead of the attenuation of X-rays, the attenuation and times of flight of ultrasonic signals in the test object are measured. With our ultrasonic CT, line scans are recorded at different angles and put together to form a cross-sectional image. In this process, the sample arranged between transmission and receiving probe is moved and turned under computer control. The overlaying of the projections of individual scans can be followed step by step on the PC.

Screenshot of the measuring software after CT scan

Screenshot of the measuring software after CT scan

In the experiment, CT scans for different settings of the transmission power and gain are recorded and comparatively analysed. The attenuation and time of flight tomograms are shown on the left in the measuring and controlling software, unfiltered at the top and mathematically filtered (contours reinforced) at the bottom. A simple form of image processing can be carried out by changing the brightness, contrast and colour.