Abstract
For breast cancer imaging, ultrasound computer tomography (USCT) is an emerging technology. To improve the image quality of our full 3-D system, a new transducer array system (TAS) design was previously proposed. This work presents a manufacturing approach which realises this new design. To monitor the transducer quality during production, the electro-mechanical impedance (EMI) was measured initially and after each assembly step. To evaluate the measured responses, an extended Krimholtz–Leedom–Matthaei (KLM) transducer model was used. The model aids in interpreting the measured responses and presents a useful tool for evaluating parasitic electric effects and attenuation at resonance. For quality control, the phase angle at thickness resonance φ t was found to be the most specific EMI property. It can be used to verify the functionality of the piezocomposites and allows reliable detection of faults in the acoustic backing. Evaluating the final response of 68 transducers showed 5% variance of the series resonance frequency. This indicates good consistency of derived ultrasound performance parameters.
Highlights
The current gold standard for early breast cancer imaging is mammography.the exposure of radiation and a limited effectiveness for dense breasts are among several disadvantages of this procedure [1,2]
The previous transducer array system (TAS) generation was based on a dice and fill process of lead-zirconium-titanate (PZT) slabs
To compare measured and modelled transducer responses, the electro-mechanical impedance (EMI) of unprocessed PZT fibre discs were measured with an impedance analyser (HP4191A, Hewlett Packard)
Summary
The current gold standard for early breast cancer imaging is mammography. the exposure of radiation and a limited effectiveness for dense breasts are among several disadvantages of this procedure [1,2]. There, different tissue types can be distinguished due to differences in speed of sound and attenuation [3,4] Conventional ultrasound devices such as hand-held probes produce anisotropic point spread functions and often lack sufficient resolution. This led to first tomographic approaches in which images are reconstructed based on 3D data acquisition [5]. This results in a sparse 3D imaging aperture which surrounds the immersed breast. We set up a well established model from literature [16] to match our initial transducer response We extended this basic model by adding additional layers to simulate the effects on the EMI introduced by each assembly step. The most specific property can be chosen to perform quality control measures during the production
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