[Ultrasound in medicine].
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Equipment Design↗
Biomedical subjects
H Ermert
Publications and source records attributed to H Ermert.
In vivo study of online liver tissue classification based on envelope power spectrum analysis.
An ultrasonic imaging and signal analysis system, combining a 3.5 MHz linear array B-scanner and an array processor, has been realized for a clinical liver tissue classification study. Based on the complete unprocessed rf data set of a real time B-image, local envelope power spectra averaged over interactively defined regions are computed. These spectra are partially corrected for several tissue type independent effects that affect comparability. A library containing the in vivo data of 65 patients with known liver tissue states in three groups (normal, cirrhotic, fat) was built up. An algorithm based on numerical optimization of parametrized spectrum characteristics combined with a k-nearest-neighbors classifier, applied to the library, leads to correct classification rates of 85.8 to 87.5 percent in discriminating pathological from normal tissue states. The method can be used for k-weighted color coded tissue type imaging with acceptable spatial resolution.
Algorithms↗
Psoriasis vulgaris in 50 MHz B-scan ultrasound--characteristic features of stratum corneum, epidermis and dermis.
One hundred and forty fully developed, non-treated plaques of psoriasis vulgaris from the arms and legs of 22 patients were examined using 50 MHz B-scan ultrasound and compared with the images from adjacent, clinically normal skin. To visualize the dermis, high pre-amplification (digitization range 200 mV) was used, determined according to A-scan images. For evaluation of epidermal phenomena, low pre-amplification (digitization range 380 mV) was chosen in order to avoid overmodulation of the skin entry echo. In 10 patients, sonographic images were compared with histological sections from the exact same planes at the same magnification. At low pre-amplification, the skin entry echo is displayed as a markedly widened, frequently interrupted band composed of spots varying in thickness, height and echo density. Within these spots, several lamellae can be observed, represented as fine, echo-rich lines stacked one upon another. These phenomena correspond histologically to focal hyperparakeratosis, scaling and cracking of the stratum corneum. Due to the low amplification of the echo-signal the dermis is not visible. High pre-amplification allows evaluation of dermal changes. Below the entry echo there is an echopoor band (EPB) corresponding to the sum of acanthosis and infiltrate in the upper dermis. Underneath the EPB the dermis is represented as a zone with scattered internal echoes which are less intense than in normal skin. Dorsal shadows are typically present. They are artifacts emanating from epidermal regions with marked hyperkeratosis and disappear when the sonographic characteristics of the epidermis are changed, for instance by application of ointments prior to sonographic examination.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
[In vivo study of the classification of diffuse liver diseases by spectral analysis of ultrasound echosignal characteristics].
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Algorithms↗
[A high-frequency ultrasound system for studying skin diseases and tumor diagnosis in dermatology].
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Fourier Analysis↗
[Ultrasound computer tomography--new image-producing possibilities].
A new technique using ultrasound computed tomography is explained. Reconstruction of pictures follows basically the algorithm of radiology CT in one plane. The computed data of several scan planes with different angles of the same subject are used for image reconstruction. In this manner, poor lateral resolution of reflections is eliminated. The improved quality of the CT ultrasound images is shown.
Breast Neoplasms↗
Lithotripsy in the common bile duct using ultrasound. Preliminary in vitro experiments.
In patients with an increased surgical risk, common bile duct stones can be removed with the aid of endoscopic papillotomy. Most stones are either passed spontaneously, or can be drawn out with the Dormia basket. Excessively large stones can first be smashed with the mechanical lithotripter. Some 20% of the stones presenting are, however, too hard to be smashed in this way. A technique was accordingly developed for smashing such bile duct stones using ultrasound. A prerequisite for this technique was the development of an acoustic wave guide that would conduct ultrasound energy even when bent. With this procedure, it will soon be possible to destroy bile duct stones in situ.
Gallstones↗
Transfer function analysis of a quasioptical ultrasonic imaging system.
The imaging properties of lenses have been well analyzed in the optical regime. However, most of these analyses have been confined to two cases: illumination of the object with ideal coherent or ideal incoherent light. In ultrasonics, imaging systems with lenses also are known. But in contrast to the optical case, the object can be easily insonified with waves of variable frequency or with a noise source of adjustable bandwidth. In this paper, the influence of the broad frequency bandwidth in an ultrasonic imaging system is emphasized. A so called "imaging channel transfer function" (ICTF) is introduced to describe all nonelectrical system properties. It is shown that the ICTF is part of a temporal frequency transfer function. This transfer function has a frequency dependence which is not readily attainable with well-known active or passive RLC-networks. Finally, it is demonstrated how to use the ICTF for calculating the image response in a wideband imaging system with ultrasonic sources emitting either deterministic or stochastic signals of a certain bandwidth.
Acoustics↗