Linear array transducers

PVDF is generally an ideal material for transducers operating at frequencies above 0.5 MHz in hydrophones and pulse echo probes for medical and nonmedical testing. A 64-element linear array transducer has been produced that, operating at 5 MHz, offers a wide-bandwidth pulse response, sharp ultrasonic field distribution, and a high energy conversion efficiency. 

A variety of linear-array transducers is currently available in the frequency range used for penile imaging. Selection of the most appropriate transducer primarily depends on the frequency, but is also related to other factors. Compared with small transducers, for instance, larger probes tend to have a large near-field beam width leading to a poor lateral resolution at shallow depths. 

Fig. 19.3a,b. Sonourethrography. Normal appearance of the urethra in sagittal (a) and transversal (b) scans. The urethra distended hy the saline solution appears as an anechoic tubular structure well depicted with linear array transducer using direct skin contact on the ventral surface of the penis and with trans-scrotal and perineal scanning for bulbar urethra... 

Doppler ultrasound is the initial modality of choice to differentiate venous malformations from other vascular abnormalities. Ultrasound is performed with a high-frequency linear array transducer (5-12 MHz). On grey-scale images, venous malformations appear as compressible hypoechoic or heterogeneous lesions [15,16] (Fig. 2.2a-c). Calcifications (demonstrated in less than 20% of cases), are quite specific of venous malformation anechoic channels can be seen. Doppler examination displays a monophasic low-velocity flow (Fig. 2.3). In 20% of venous malformations, no flow can be demonstrated. Dynamic manoeuvres such as Valsalva or manual compression are sometimes necessary to induce a visible Doppler flow. 

E Kimura, N. Hashimoto. and H. Ohigashi. Performance of a linear array transducer of vinylidene fluoride trifluorocthyleiK copolymer, IEEE Trans. Sanies and Ultrasonics SU-32 566 (1965). 

An adequate assessment of the subcutaneous tissue can be efficiently performed be means of less specialized high-resolution transducers chararter-izedby the same frequency range (5-15 MHz) appropriate for other musculoskeletal examinations. The type and frequency of the selected transducer vary depending on the region of the body to be examined. For the thin subcutaneous tissue of the dorsum of the hand and wrist, linear-array transducers working at a center frequency >7.5-10 MHz are the most appropriate. Superficial focusing capabilities and a thin... 

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