Breast Ultrasound Technology and Performance Evaluation of Ultrasound Equipment: B-Mode

Fabrication and evaluation of breast tissue equivalent phantoms for image quality assessment in ultrasound imaging

INTRODUCTION

Phantom materials with tissue-equivalent physical properties that require regular evaluation using patented phantoms are essential for medical device quality assurance programs. This study evaluated phantom materials for tissue equivalence and their use in image quality assessment for breast ultrasound scanner performance testing using two custom-made phantoms.

METHODS

Two types of phantoms were developed: phantoms A and B. Phantom A was made from a base material consisting of polyvinyl chloride-plastisol with the addition of glycerol, whereas phantom B consisted of polyvinyl chloride-plastisol with the addition of graphite. Each phantom had a stiff and soft lesion shaped like a sphere, with a diameter of 1.4 cm. The phantoms were cuboids with dimensions of 10 × 10 cm2 and a thickness of 5 cm. A series of phantom evaluations was performed, consisting of density, elasticity, acoustic properties, B-mode ultrasound images, and strain ratio.

RESULTS

The characterisation results show that background A closely resembles fibroglandular tissue in terms of density and acoustic properties (<5% variation); background B only resembles fibroglandular tissue in terms of density (-1.8% variation). In terms of elasticity, both backgrounds were close to the minimum value of fibroglandular tissue elasticity. The soft lesion on the phantom had a slightly lower density and elasticity than the carcinoma, whereas its acoustic properties (speed of sound and attenuation coefficient) were slightly higher than those of the reference carcinoma. Both phantoms were consistent with the literature in terms of strain ratio, geometric accuracy, lesion detection, and mean pixel value and showed good potential stability over one year.

CONCLUSION

This study successfully described the fabrication and evaluation sequence of a phantom equivalent to breast fibroglandular tissue and its evaluation via ultrasound imaging.

IMPLICATIONS FOR PRACTICE

This study offers proprietary information essential for the fabrication of phantoms that can be used for quality assurance and control in ultrasound imaging.

MEMS Acoustic Sensors: Charting the Path from Research to Real-World Applications

MEMS acoustic sensors are a type of physical quantity sensor based on MEMS manufacturing technology for detecting sound waves. They utilize various sensitive structures such as thin films, cantilever beams, or cilia to collect acoustic energy, and use certain transduction principles to read out the generated strain, thereby obtaining the targeted acoustic signal's information, such as its intensity, direction, and distribution. Due to their advantages in miniaturization, low power consumption, high precision, high consistency, high repeatability, high reliability, and ease of integration, MEMS acoustic sensors are widely applied in many areas, such as consumer electronics, industrial perception, military equipment, and health monitoring. Through different sensing mechanisms, they can be used to detect sound energy density, acoustic pressure distribution, and sound wave direction. This article focuses on piezoelectric, piezoresistive, capacitive, and optical MEMS acoustic sensors, showcasing their development in recent years, as well as innovations in their structure, process, and design methods. Then, this review compares the performance of devices with similar working principles. MEMS acoustic sensors have been increasingly widely applied in various fields, including traditional advantage areas such as microphones, stethoscopes, hydrophones, and ultrasound imaging, and cutting-edge fields such as biomedical wearable and implantable devices.

Technical assessment of resolution of handheld ultrasound devices and clinical implications

PURPOSE

Since handheld ultrasound devices are becoming increasingly ubiquitous, objective criteria to determine image quality are needed. We therefore conducted a comparison of objective quality measures and clinical performance.

MATERIAL AND METHODS

A comparison of handheld devices (Butterfly IQ+, Clarius HD, Clarius HD3, Philips Lumify, GE VScan Air) and workstations (GE Logiq E10, Toshiba Aplio 500) was performed using a phantom. As a comparison, clinical investigations were performed by two experienced ultrasonographers by measuring the resolution of anatomical structures in the liver, pancreas, and intestine in ten subjects.

RESULTS

Axial full width at half maximum resolution (FWHM) of 100µm phantom pins at depths between one and twelve cm ranged from 0.6-1.9mm without correlation to pin depth. Lateral FWHM resolution ranged from 1.3-8.7mm and was positively correlated with depth (r=0.6). Axial and lateral resolution differed between devices (p<0.001) with the lowest median lateral resolution observed in the E10 (5.4mm) and the lowest axial resolution (1.6mm) for the IQ+ device. Although devices showed no significant differences in most clinical applications, ultrasonographers were able to differentiate a median of two additional layers in the wall of the sigmoid colon and one additional structure in segmental portal fields (p<0.05) using cartwheel devices.

CONCLUSION

While handheld devices showed superior or similar performance in the phantom and routine measurements, workstations still provided superior clinical imaging and resolution of anatomical substructures, indicating a lack of objective measurements to evaluate clinical ultrasound devices.

Image quality evaluation of ultrasound imaging systems: advanced B-modes

The Quality assurance of ultrasound clinical imaging systems is essential for maintaining their performance to the highest level and for complying with the requirements by various regulatory and accrediting agencies. Although there is no standardization yet, most of the quality assessment procedures available in literature are proposed for B-mode and Doppler imaging. However, ultrasound imaging systems offer a variety of advanced imaging modes, besides B-mode and Doppler, which are primarily aimed at improving image quality. This study presents computer-based methods for evaluating image quality for the advanced imaging modes of ultrasound imaging systems: harmonic imaging, spatial compounding imaging, adaptive speckle reduction, and tissue aberration correction. The functions and parameters proposed for evaluating image quality are: grayscale mapping function, image contrast, contrast-to-noise ratio (CNR), and high-contrast spatial resolution. We present our computer-based methods for evaluating image quality of these modes with a number of probe and scanner combinations, which were employed to image targets in ultrasound phantoms. The functions and parameters here proposed in image quality performance evaluation are: grayscale mapping function, image contrast, CNR, and high-contrast spatial resolution. We show that these quantities could be useful in developing standardized methods for evaluating the advanced ultrasound imaging modes, especially when the advanced mode resulted in subtle visual differences.