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This paper presents the acoustical design, manufacture and evaluation of an ultrasound catheter array for endobronchial imaging. In order to be used in an existing bronchofiberscope, the 64 elements transducer is included in a 7 French (2.3 mm Outer Diameter) catheter, using a ribbon-based cabling technology. The ultrasound array has a 200 µm pitch, a 1.5 mm elevation, and operates at 10 MHz center frequency. The piezoelectric material is based on 1-3 piezo-composite technology and the front layer (optimized multilayer stack of passive materials) is selected to act both as a matching and protection layer. The probe is integrated into the 7 French catheter and interfaced to a commercial ultrasound system. Besides the manufacturing process of the whole transducer, the paper reviews electro-acoustical characteristics including sensitivity, frequency, bandwidth and homogeneity performances. The aim of this probe is the detection of epithelial abnormalities, transparietal extension of lesions and detection of lymph nodes related to local cancer. Finally, in vivo images obtained through a bronchofiberscope are presented and discussed from a clinical point of view.

This feasibility study shows that the prototype probe can be used to depict pulmonary lesions and to guide biopsy nodes. Larger series are needed to validate its usefulness in clinical work-ups and patients management.

Recent advances in ultrasound medical imaging such as contrast agent, harmonic or sonar type imaging require ultrasound arrays with higher electro-acoustical and acoustical performances than the standard state of the art. Higher bandwidth, higher sensitivity, better resolution and improved beam characteristics are necessary to improve image quality. This paper presents two different configurations of array transducers: a 3.5 MHz center frequency curved linear array for general purpose, abdominal and obstetric imaging and a 7 MHz center frequency linear array for small parts and peripheral vascular imaging. Both arrays include optimized 1-3 piezocomposite material based on high dielectric permittivity piezoceramic. These arrays that use new acoustic matching design exhibit a higher bandwidth with a +15% to 25% gain compared to standard ones with high resolution resulting in a wide operating frequency range. Complete electroacoustic and acoustic evaluations of both arrays are presented in this paper. To characterize and evaluate the electroacoustic performances, we propose to set a figure of merit.

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