Annular Array Probe Research Articles

Feasibility of Backscattering Coefficient Evaluation of Soft Tissue Using High-Frequency Annular Array Probe

The objective of this work is to address the need for versatile and effective tissue characterization in abdominal ultrasound diagnosis using a simpler system. We evaluated the backscattering coefficient (BSC) of several tissue-mimicking phantoms utilizing three different ultrasonic probes: a single-element transducer, a linear array probe for clinical use, and a laboratory-made annular array probe. The single-element transducer, commonly used in developing fundamental BSC evaluation methods, served as a benchmark. The linear array probe provided a clinical comparison, while the annular array probe was tested for its potential in high-frequency and high-resolution ultrasonic observations. Our findings demonstrate that the annular array probe meets clinical demands by providing accurate BSC measurements, showcasing its capability for high-frequency and high-resolution imaging with a simpler, more versatile system.

Ocular Ultrasound, a neglected tool in the diagnosis of central retinal artery occlusion.

Purpose: To discuss the practical utility of ocular ultrasound in central retinal artery occlusion (CRAO). Methods: Ocular ultrasound was obtained in 4 patients with CRAO using a 20 MHz Annular Array Probe of the ABSolu (Quantel Medical, Texas, USA) ultrasound machine. Results: The causative embolus occluding the central retinal artery was detected on ocular ultrasound imaging in four patients with CRAO. Conclusion: Ocular ultrasound, including newer generation, higher frequency ultrasound probes, aids in the detection of the “retrobulbar spot sign”, a finding that seems to be related to embolic central retinal artery occlusion. This sign will orient investigations towards finding an embolic source.

Development of the 64-channel annular array probe with sector scan

Development of the 64-channel annular array probe with sector scan

Improved High-Resolution Ultrasonic Imaging of the Eye

Currently, virtually all clinical diagnostic ultrasound systems used in ophthalmology are based on fixed-focus, single-element transducers. High-frequency (> or = 20-MHz) transducers introduced to ophthalmology during the last decade have led to improved resolution and diagnostic capabilities for assessment of the anterior segment and the retina. However, single-element transducers are restricted to a small depth of field, limiting their capacity to image the eye as a whole. We fabricated a 20-MHz annular array probe prototype consisting of 5 concentric transducer elements and scanned an ex vivo human eye. Synthetically focused images of the bank eye showed improved depth of field and sensitivity, allowing simultaneous display of the anterior and posterior segments and the full lens contour. This capability may be useful in assessment of vitreoretinal pathologies and investigation of the accommodative mechanism.

Treatment of localised prostate cancer with transrectal high intensity focused ultrasound

With the advent of PSA dosing, an increasing number of prostate cancers are being detected at a local stage. Since 1989, our group has been developing a research project with the aim of establishing treatment of localised prostate cancer by means of HIFU. The treatment is performed transrectally, using ultrasound imaging guidance only. The quality of HIFU treatment depends on four factors: the intensity of the transmitted pulse, the exposure time, the signal frequency, and the time between two firing bursts. The lesions are created by a thermal effect. Their slightly conical form is due to the absorption of ultrasound by tissue, enhanced by cavitation bubbles. Results obtained since 1993 demonstrate that transrectally administered HIFU treatment achieves local control of localised prostate cancer in 80% of cases, with 70% complete success and 30% partial response. The use of an annular array probe with variable focus and frequency should significantly improve results in the future. Finally, real time visual display of the damaged tissue via differential imaging of the attenuation coefficient should give the surgeon an instant appreciation of the result of the sequence. It would thus be possible to repeat treatment of insufficiently covered zones in the same session.

Equine cardiac studies with annular array probe technology

Equine cardiac studies with annular array probe technology

134. 表在性疾患におけるアニュラアレイプローブの有用性(超音波 基礎)

従来のリニアプローブに比べて方位分解能・距離分解能コントラスト分解能などの各種分解能が、大幅にアップしているため診断基準である所見の、形状・辺縁・境界エコー・内部エコー・後方エコーなど多くの所見が得られるため診断能が向上した。また、これからの課題としてアニュラアレイプローブは視野深度が5cmと浅いため、その対象が体表臓器に限られてしまうが、今後、腹部領域への応用を期待する。

Simulating annular array probe performance by ray tracing

The imaging performance of annular array probes has been simulated by a ray tracing method. A particular strength of the method is the ability to account for refraction and attenuation of materials between the transducer and the imaging point, including coupling fluid, probe cap, and tissue layers. Rays are traced from the surface of the transducer to the field point under consideration. The aperture function, real and imaginary parts, is reconstructed as seen from that point. Beam profiles are determined by a Fourier transform of the aperture function. Electronic functions, such as time delay focusing, apodization, errors in gain, and time delay, can be simulated by modifying the aperture function appropriately. Examples are given of nonspherical geometry and effects of subcutaneous fat layer. Apodization is shown to require extremely tight phase control, both across transducer elements and in focusing accuracy.

In vitro estimation and imaging of attenuation coefficients and instantaneous frequency for breast tissue characterization

For breast tissue characterization, three acoustic parameters, integrated attenuation coefficient(IAC), frequency-dependent attenuation coefficient(FDAC and instantaneous frequency(IF), were estimated in vitro and processed to make images of these parameters for resected human breast specimens. Experimental system with a 5 MHz center frequency was used and the same estimating and imaging system was connected with a clinical diagnostic device with a 7.5 MHz annular array probe (Aloca SSD 270) for in vivo type studies. To estimate these parameters, fast Fourier transform and spectral difference method were adopted for IAC and FDAC and the Hilbert transform for IF. Large statistical variances were found in the estimated values of these parameters. These dispersions of data may be due to insufficient size and tissue heterogeneity of the breast specimens. Additional miscellaneous problems may be involved. However, all of these can be, in part, overcome by averaging procedures. The significance of estimating and imaging these parameters for breast tissue characterization was discussed.