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Parametry stosowane do oceny obrazów ultrasonograficznych wysokich częstotliwości skóry

Wawrzyniak Z. M., Malinowska S., Mlosek R.K.

Inżynier i Fizyk Medyczny

2013

Vol. 2, nr 4

222--226

Badania ultrasonograficzne wysokich częstotliwości skóry wykonywane są za pomocą klasycznych ultrasonografów, wyposażonych w głowice o częstotliwościach powyżej 20 MHz lub aparatów wysokich częstotliwości dedykowanych do tego celu. Stosowane do badań aparaty pozwalają obrazować skórę w wysokiej rozdzielczości i oceniać struktury o wielkości lub grubości mniejszej niż 0,1 mm. Ultrasonograficzne obrazowanie skóry wykorzystywane jest głównie do monitorowania przebiegu leczenia chorób skóry, tj. twardziny, łuszczycy oraz do oceny zmian ogniskowych. Ultrasonografia skóry znalazła również zastosowanie w medycynie estetycznej i kosmetologii, gdzie służy do oceny stanu skóry oraz monitorowania prowadzonych terapii. Obecnie ultrasonograficzne obrazy skóry ocenianie są w oparciu o analizę jakościową (ocena wizualna) oraz analizę ilościową – pomiary grubości poszczególnych struktur, pola powierzchni oraz echogeniczności. W analizie obrazów USG szczególnie użytecznym parametrem jest echogeniczność i wynikająca z niej ocena obrazu. Sposób wyznaczania i interpretowania tego parametru w przypadku badań skóry nie został jednak dotychczas szczegółowo opisany, dlatego też istotne jest prowadzenie prac badawczych mających na celu opracowanie parametrów do oceny skóry na obrazach ultrasonograficznych.

Skin ultrasound scans are taken using conventional ultrasound devices, equipped with > 20 MHz probes or high frequency (HF) ultrasound devices intended for skin testing. The ultrasound scanning devices allow for high resolution skin imaging and assessment of structures smaller/thinner than 0,1 mm. Ultrasound skin imaging is used in dermatology for treatment monitoring in patients with scleroderma, psoriasis or for the assessment of focal lesions. It has also proved to be useful in aesthetic medicine and cosmetology, for skin assessment and treatment monitoring. Currently, skin ultrasound scans are subjected both to qualitative (i.e. visual assessment) and quantitative (i.e. thickness of individual structures, areas and echogeneity measurements) analyses. The echogeneity parameter is particularly useful in ultrasound image assessment. However, the methodology for determining and interpreting this parameter in skin ultrasound scanning has not been described yet, therefore it is crucial to conduct further studies aiming at developing parameters of ultrasound skin assessment.

Thick Film Transducers for High Frequency Coded Ultrasonography

Nowicki A., Lewandowski M., Wójcik J., Tymkiewicz R., Lou-Moller R., Wolny W., Zawada T.

Archives of Acoustics

2011

Vol. 36, No. 4

945-954

Recently a new technology of piezoelectric transducers based on PZT thick film has been developed as a response to a call for devices working at higher frequencies suitable for production in large numbers at low cost. Eight PZT thick film based focused transducers with resonant frequency close to 40 MHz were fabricated and experimentally investigated. The PZT thick films were deposited on acoustically engineered ceramic substrates by pad printing. Considering high frequency and nonlinear propagation it has been decided to evaluate the axial pressure field emitted (and reflected by thick metal plate) by each of concave transducer differing in radius of curvature – 11 mm, 12 mm, 15 mm, 16 mm. All transducers were activated using AVTEC AVG-3A-PS transmitter and Ritec diplexer connected directly to Agilent 54641D oscilloscope. As anticipated, in all cases the focal distance was up to 10% closer to the transducer face than the one related to the curvature radius. Axial pressure distributions were also compared to the calculated ones (with the experimentally determined boundary conditions) using the angular spectrum method including nonlinear propagation in water. The computed results are in a very good agreement with the experimental ones. The trans- ducers were excited with Golay coded sequences at 35–40 MHz. Introducing the coded excitation allowed replacing the short-burst transmission at 20 MHz with the same peak amplitude pressure, but with almost double center frequency, resulting in considerably better axial resolution. The thick films exhibited at least 30% bandwidth broadening comparing to the standard PZ 27 transducer, resulting in an increase in matching filtering output by a factor of 1.4–1.5 and finally resulting in a SNR gain of the same order.

Enamel thickness measurement with a high frequency ultrasonic transducer-based hand-held probe for potential application in the dental veneer placing procedure

Ślak B., Ambroziak A., Strumban E., Maev R.Gr.

Acta of Bioengineering and Biomechanics

2011

Vol. 13, no. 1

65-70

This study presents a novel approach to measure the enamel thickness potentially applicable to the veneer placing procedure. All experiments have been carried out on the extracted human teeth, using a high frequency ultrasonic transducer (50 MHz, Sonix, Springfield, VA, USA). The enamel thickness measurement results obtained with high positional accuracy by a scanning acoustic microscope (Tessonics AM1103, Windsor, ON, Canada) were compared with the measurements conducted in a hand-held mode by using the same transducer placed in a custom fixture. Finally, to validate the ultrasonic measuring results, the samples were cut down the long axis to expose the cross-section. The enamel thickness was measured in several points along the selected part of the exposed cross-section by using an optical microscope (Stemi SV 11, Carl Zeiss AG, Jena, Germany). The values of the enamel thickness received by using the hand-held probe vs. the acoustic microscope were in close proximity (about 10% difference) and were also satisfactory close to the enamel thickness results obtained from the direct cross-sectional measurements (about 12% difference). The authors suggested a measuring procedure that allows avoiding errors related to the ultrasonic beam localization on the tooth surface. The high feasibility of the ultrasonic pulseecho measurements in a hand-held mode was demonstrated.