A main drawback of 20-25 MHz ultrasound units for skin imaging is their limited resolution. We used a transducer with a center frequency of 95 MHz and a resolution of 8.5 microm axially and 27 microm laterally - an almost 10-fold increase compared with 20 MHz. By means of a new scanning technology we reached a depth of field of 3.2 mm. We examined normal palmar skin, normal glabrous skin on the abdomen, the upper back, the calf and the dorsal forearm, and 35 lesions of psoriasis vulgaris. From 11 psoriatic plaques biopsies were taken for correlation with the sonograms. In normal palmar skin, the horny layer is represented as an echopoor band below the skin entry echo, traversed by echorich coils, which correspond to eccrine sweat gland ducts. The thickness of this band significantly increases after occlusive application of petrolatum. Its lower border is defined by an echorich line, representing the stratum corneum/stratum Malpighii-interface. Underneath, a second echopoor band is visible, which corresponds to the viable epidermis plus the papillary dermis, bordered by the scattered echo reflexes of the reticular dermis. This band is also visible in glabrous skin; however, the stratum corneum cannot be detected. In psoriatic lesions, the thickened horny layer appears echorich; after application of petrolatum, its echodensity decreases. Below, the acanthotic epidermis plus the dermis with the inflammatory infiltrate are represented as an echopoor band. There is an excellent correlation between the sonometric thickness of this band and the histometric thickness of the acanthosis plus the infiltrated dermis. Our results show that 100 MHz sonography is a valuable tool for in vivo examination of the upper skin layers.
Analysis of agreement clearly demonstrated that the performance of 100-MHz ultrasound is superior to conventional 20-MHz ultrasound, even though a relatively small positive bias was observed in 100-MHz ultrasound, indicating a systematic error. We consider 100-MHz ultrasound a useful tool for the noninvasive determination of TT of thin MSL in vivo.
High frequency and broadband ultrasound in the frequency range above 20 MHz is an efficient modality for the non invasive and high resolution imaging of skin structures and skin diseases like skin tumors and inflammatory processes. However, special system designs and signal processing strategies have to be applied to account for the strong and frequency dependent attenuation of high frequency ultrasound in tissue. In this paper the design of an ultrasound imaging system with a minimum spatial resolution of about 9, utilizing the frequency range from 30 to 150 MHz, is presented. This system enables the high resolution visualization of the uppermost skin layers, which is of great interest in dermatology and cosmetics. To quantify the imaging properties of the system reference measurements were performed by imaging a glass plate and a wire phantom. Furthermore, image processing techniques for the analysis of three dimensional data sets were adapted to investigate the topology of skin structures like skin layers. Results from in vivo measurements on healthy skin and skin tumors are presented.
ÜbersichtHochfrequenter und breitbandiger Ultraschall im Frequenzbereich oberhalb von 20 MHz stellt eine leistungsfä-hige Modalität zur nichtinvasiven und hochauflösenden Abbildung von Hautstrukturen und Hauterkrankungen wie Hauttumoren und entzündlichen Prozessen dar. Es müssen jedoch spezielle Systemkonzepte und Signalverarbeitungstechniken angewandt werden, um der starken und frequenzabhängigen Dämpfung des hochfrequenten Ultraschalls im Gewebe Rechnung zu tragen. In dieser Arbeit wird der Entwurf eines Ultraschallabbildungssystems, das den Frequenzbereich von 30 bis 150 MHz nutzt, mit einer kleinsten räumlichen Auflösung von etwa 9 vorgestellt. Dieses System erlaubt die hochauflösende Darstellung der obersten Hautschichten, was von großem Interesse in der Dermatologie und der Kosmetik ist. Zur Quantifizierung der Abbildungseigenschaften des Systems wurden Referenzmessungen durch Abbildung einer Glasplatte und eines Drahtphantoms durchgeführt. Femer wurden Bildverarbeitungstechniken für die Analyse dreidimensionaler Datensätze adaptiert, um die Topologie von Hautstrukturen (Hautschichten, Haarfollikel) zu untersuchen. Es werden Ergebnisse von Messungen in vivo an gesunder Haut und an Hauttumoren vorgestellt. Für die Dokumentation Hochfrequenter Ultraschall / Ultraschallabbildung / Medizin / Dermatologie / Haut / B/D-scan
The decision for endoscopic or surgical excision of adenomas is determined by general health status, histology, size, location, and depth of the lesion. In carcinoma of the papilla of Vater it is important to assess the tumoral ductal infiltration correctly to determine whether endoscopic resection is a viable option. Intraductal ultrasound is essential before initiating treatment and it therefore contributes to conservative therapy in patients with tumors of the papilla of Vater. Temporary placement of a short pancreatic duct stent may protect against pancreatitis and might allow more excessive ablation of adenomatous tissue, especially around the pancreatic duct orifice. After endoscopic sphincterotomy, biliary and pancreatic endoprostheses can be inserted easily in cases of obstructed pathways or cholangitis and pancreatitis due to tumor obstruction. Argon plasma coagulation can be used to treat oozing tumor hemorrhages or to vaporize tumoral residues after endoscopic snare resection. Endoscopic surveillance is essential after surgical or endoscopic resection of adenomas of the papilla of Vater.
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