Transducer Handle Research Articles

Novel Technique for Transducer Handling in Sterile Ultrasound Guided Procedures

The objective of this paper is to describe a novel technique for handling an ultrasound transducer while performing sterile ultrasound guided procedures. This novel technique involves placement of the transducer inside the sterile glove on the hand of the operator. This technique allows the operator access to use of both hands without having to pass the transducer to an assistant.

Use of arm-free devices in bovine reproductive ultrasound

Ultrasonography has been employed in bovine practice since the 1980s for visualizing and evaluating the reproductive tract, diagnosing pregnancy, identifying anomalies, and determining the age and gender of a fetus. The modality has advanced quickly since then, introducing new technologies, techniques, and equipment to facilitate its use and improve its accuracy and efficacy. Among these advancements is the advent of arm-free ultrasound with the use of a transducer handle, which allows the user to conduct an ultrasound exam without inserting his or her arm into the rectum of the animal. The intention is to increase exam speed, decrease animal discomfort, improve reach, and reduce chronic and overuse injuries to the operator. We conducted a survey to determine why and how ultrasonographers employ this tool, whether they had experienced any negative consequences from its use, and what effect it has on their reproductive practice.

Detection of Coronary Arteries and Evaluation of Anastomoses with a Commercially Available 15-MHz, Broadband, Linear Array Transducer

In coronary artery bypass surgery the detection of the target vessels can be difficult due to their intramural location, coverage by adipose tissue, calcification, or fibrous tissue formation. Their identification is especially critical during off-pump coronary artery bypass (OPCAB) and minimally invasive direct coronary artery bypass (MIDCAB) surgeries. Our objectives were to identify whether (1) the epimyocardial use of the broadband linear array transducer CL15-7 allows a clear and rapid identification of the target artery during on-pump coronary bypass (CPB), OPCAB and MIDCAB surgeries; and (2) if this transducer is helpful in investigating the anastomotic morphology with 2D and color flow Doppler. Thirty-two patients without a visually identifiable left anterior descending artery (LAD) were included in the study and epimyocardial ultrasonography was performed. Stabilization of the beating heart was used in 19 patients; in 13 patients, the surgery was carried out with CPB on the arrested heart. Two-dimensional ultrasound alone, or in combination with color Doppler, was used to identify the affected vessel as well as a suitable anastomosis site. Pulsed wave Doppler had to be used occasionally to differentiate between artery and vein. Patency of the anastomoses was established with color Doppler immediately after reinitiating blood flow. An evaluation of the distal graft diameter, its length, and the quality of the anastomosis was made with 2D and color Doppler. Transit-time Doppler flow was used to confirm patency. The LAD could be identified ultrasonographically in all 32 patients at a depth of 3 to 15 mm. The right coronary artery (RCA) was located at a depth of 3 to 10 mm in the 5 patients where this vessel was to be bypassed. The coronary arteries located on the lateral or posterior aspect of the heart could not be reached due to the shape and rigidity of the transducer handle. The intended anastomosis sites of the LAD and RCA were identified with ultrasound according to their topography and morphology. In all cases the vessel could be dissected and bypassed without undue damage or bleeding. In one OPCAB patient, the LAD was identified in close proximity to the overlying vein along the whole of the anterior wall. This resulted in conversion to CPB, thus facilitating secure exposure of the LAD. The ultrasonographic visibility of the left internal mammary artery to LAD and saphenous vein graft to RCA anastomoses was excellent, and patency correlated well with the transit time flow measurements. The CL15-7 transducer gives excellent near field visibility of the LAD and RCA. This is extremely valuable for the safe dissection of these vessels, especially during off-pump coronary surgery. The anatomical morphology of the anastomoses can be identified but, due to the shape of the transducer handle, only the coronary arteries on the anterior surface of the heart can be evaluated. A flexible, rather than a rigid, hockey stick-shaped handle would eliminate this problem. Training is essential to obtain reliable results.

Place of an Ultrasonography Simulator in Ultrasonography Training for Fertility Nurses

Ultrasonography has a vital place in British fertility units, where it is commonly performed by nurses. This study evaluated the place of an ultrasonography simulator (Ultrasim) in ultrasonography training particularly for fertility nurses. Thirty-one participants took part in evaluation of the ultrasound simulator—two doctors, two ultrasonographers, and 27 fertility nurses and midwives with varying level of ultrasonography expertise. After using the simulator, participants were asked to give their opinion on the realism of the simulator and its potential as a training tool. All the 29 responding participants reported that the mannequin was easy to scan and suitable for training. Most participants found the mannequins (29 of 31 respondents) and transducer handling (27 of 29 respondents) to be satisfactory or greater than satisfactory. All 31 participants were satisfied with the image recognition training ability. Most participants felt that Ultrasim has a place in ultrasound training (29 of 31 respondents). Compared with ultrasound machines used routinely in fertility clinics this study suggests that the Ultrasim simulator has realistic controls and image quality with a place in the future training of fertility nurses.

US of the Rotator Cuff: Pitfalls, Limitations, and Artifacts

High-resolution ultrasonography (US) has gained increasing popularity as a diagnostic tool for assessment of the soft tissues in shoulder impingement syndrome. US is a powerful and accurate method for diagnosis of rotator cuff tears and other rotator cuff abnormalities, provided the examiner has a detailed knowledge of shoulder anatomy, uses a standardized examination technique, and has a thorough understanding of the potential pitfalls, limitations, and artifacts. False-positive sonographic findings of rotator cuff tears can be caused by the technique (anisotropy, transducer positioning, acoustic shadowing by the deltoid septum), by the anatomy (rotator cuff interval, supraspinatus-infraspinatus interface, musculotendinous junction, fibrocartilaginous insertion), or by disease (criteria for diagnosis of rotator cuff tears, tendon inhomogeneity, acoustic shadowing by scar tissue or calcification, rotator cuff thinning). False-negative sonographic findings of rotator cuff tears can be caused by the technique (transducer frequency, suboptimal focusing, imaging protocol, transducer handling), by the anatomy (nondiastasis of the ruptured tendon fibers, posttraumatic obscuration of landmarks), by disease (tendinosis, calcifications, synovial proliferation, granulation or scar tissue, bursal thickening, massive rotator cuff tears), or by patient factors (obesity, muscularity, limited shoulder motion).

Ultrasonic imaging using a 5-MHz multilayer/single-layer hybrid array for increased signal-to-noise ratio

Conventional diagnostic ultrasound scanners are bulky and require significant amounts of electrical power during operation. Reducing the size, weight, and consumption of electrical power is made easier through the use of highly integrated compact transmit and receive electronics that may be incorporated in the transducer handle. This necessitates the use of low voltage transmitters and low power receive preamplifiers. Conventional scanners typically use approximately 100-V pulses during transmit; therefore, decreasing the transmit voltage to 15 V decreases the transmit sensitivity. Conventional receive electronics that are located at the scanner degrade the received signal-to-noise ratio (SNR) because the array element cannot efficiently drive the coaxial cable. Transmit sensitivity and received SNR can be radically improved using a multilayer/single-layer hybrid array making integration of electronics into the transducer handle more feasible. In this paper, we discuss the design, fabrication, and testing of a 5-MHz hybrid linear array. The hybrid array included 16 multilayer transmit elements (10 Omega impedance) and 24 single-layer receive elements at a half wavelength element pitch. Low voltage transmitters with an output resistance of 7 Omega and high impedance JFET preamplifiers using 15 V for biasing were located adjacent to the hybrid array in the transducer handle. The transmit sensitivity and received SNR of the hybrid array were compared with a conventional array using 50-Omega transmitters and receive preamplifiers at the scanner. The transmit sensitivity improved by 12.8 dB, and the received SNR improved by 7.8 dB, yielding an overall improvement of 20.6 dB, which compared well with predictions from the KLM model. Images of phantoms and in vivo images of the kidney obtained with the Siemens Model 1200 phased array system showed the increased SNR using the hybrid array. Estimates of penetration in tissue mimicking phantoms (alpha=0.5 dB/(cm MHz)) improved by 7 cm compared with the control.

Ultrasonographic evaluation of equine tendons: a quantitative in vitro study of the effects of amplifier gain level, transducer-tilt, and transducer-displacement.

The objective of the in vitro experiments described in this paper was to quantify the effects of some instrumental variables on the quantitative evaluation, by means of first-order gray-level statistics, of ultrasonographic images of equine tendons. The experiments were done on three isolated equine superficial digital flexor tendons that were mounted in a frame and submerged in a waterbath. Sections with either normal tendon tissue, an acute lesion, or a chronic scar, were selected. In these sections, the following experiments were done: 1) a gradual increase of total amplifier gain output subdivided in 12 equal steps; 2) a transducer tilt plus or minus 3 degrees from perpendicular, with steps of 1 degree; and 3) a transducer displacement along, and perpendicular to, the tendon long axis, with 16 steps of 0.25 mm each. Transverse ultrasonographic images were collected, and in the regions of interest (ROI) first-order gray-level statistics were calculated to quantify the effects of each experiment. Some important observations were: 1) the total amplifier gain output has a substantial influence on the ultrasonographic image; for example, in the case of an acute lesion, a low gain setting results in an almost completely black image; whereas, with higher gain settings, a marked "filling in" effect on the lesion can be observed; 2) the relative effects of the tilting of the transducer are substantial in normal tendon tissue (18%) and chronic scar (12%); whereas, in the event of an acute lesion, the effects on the mean gray level are dramatic (40%); and 3) the relative effects of displacement of the transducer are small in normal tendon tissue, but on the other hand, the mean gray-level changes 7% in chronic scar, and even 20% in an acute lesion. In general, slight variations in scanner settings and transducer handling can have considerable effects on the gray levels of the ultrasonographic image. Furthermore, there is a strong indication that this quantitative method, as far as based exclusively on the first-order gray-level statistics, may be not discriminative enough to accurately assess the integrity of the tendon. Therefore, the value of a quantitative evaluation of the first-order gray-level statistics for the assessment of the integrity of the equine tendon is questionable.

Hybrid multi/single layer array transducers for increased signal-to-noise ratio

In medical ultrasound imaging, two-dimensional (2-D) array transducers are necessary to implement dynamic focusing in two dimensions, phase correction in two dimensions and high speed volumetric imaging. However, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance, which decreases the transducer signal-to-noise ratio (SNR). We have previously shown that SNR is improved using transducers made from multi-layer PZT, due to their lower electrical impedance. In this work, we hypothesize that SNR is further increased using a hybrid array configuration: in the transmit mode, a 10 Omega electronic transmitter excites a 10 Omega multi-layer array element; in the receive mode, a single layer element drives a high impedance preamplifier located in the transducer handle. The preamplifier drives the coaxial cable connected to the ultrasound scanner. For comparison, the following control configuration was used: in the transmit mode, a 50 Omega source excites a single layer element, and in the receive mode, a single layer element drives a coaxial cable load. For a 5x102 hybrid array operating at 7.5 MHz, maximum transmit output power was obtained with 9 PZT layers according to the KLM transmission line model. In this case, the simulated pulse-echo SNR was improved by 23.7 dB for the hybrid configuration compared to the control. With such dramatic improvement in pulse-echo SNR, low voltage transmitters can be used. These can be fabricated on integrated circuits and incorporated into the transducer handle.

Optoelectronic transmitters for medical ultrasound transducers

Optoelectronics and fiber optics can be used to miniaturize and improve the flexibility of the transducer cable and transducer handle of medical diagnostic ultrasound scanners. The reduction in size has gained importance as 2-D array transducers with up to 1000 independent channels become accepted to improve diagnostic ultrasound images. The authors describe the analysis, design, fabrication and testing of a prototype silicon photoconductive semiconductor switch (PCSS). The monolithic silicon PCSS was used in combination with an infrared semiconductor diode laser with a fiber optic "pigtail" to shock excite and burst excite a 2-D array transducer element resonant at 2.5 MHz. Optically controlled voltage, current, and ultrasound pulses are compared to those from conventional electronic shock excitation and narrow band Doppler pulses. The optically triggered ultrasound pulse for single shock excitation produced 30 V spikes at the 2-D array element with a fall time of 200 nsec and a rise time of 2 /spl mu/sec with a peak current through the transducer element of 34 mA. An optically produced burst of eight pulses at a frequency of 2.5 MHz produced 11 V spikes at the transducer with a fall time under 100 nsec and a rise time of approximately 300 nsec. The peak current per pulse was 25 mA through the transducer element. These results show the feasibility of applying optoelectronic technology to replace conventional electronic transmitter technology.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Two-dimensional arrays for medical ultrasound

The design, fabrication and evaluation of two-dimensional transducer arrays are described for medical ultrasound imaging. A 4 × 32, 2.8 MHz array was developed to use new signal processing techniques for improved B-scan imaging including elevation focusing, phase correction and synthetic aperture imaging. Laboratory measurements from typical array elements showed 50 Ω insertion loss of -56ddB, -6 dB fractional bandwidth of 43%, interelement crosstalk of -19 dB, and -6 dB pulse-echo angular response of 62°. Simulations of pulse-echo beam plots have shown grating lobes 20 dB below the main lobe at ±7° in the elevation direction. The complete 2-D array has been used for measurements of phase aberrations in breast, and the individual 32 element linear arrays have been used to obtain conventional B-scans. Several 16 × 16 arrays have also been developed for high speed volumetric imaging. These include 96 transmit elements and 32 receive channels. With a λ/4 matching layer, laboratory measurements show 50 Ω insertion loss of -72 dB, -6 dB fractional bandwidth of 63%, interelement crosstalk of -29 dB and -6 dB angular response of 25°. Pulse-echo sensitivity was improved by 21 dB through the use of integrated circuit preamplifiers of high impedance mounted in the transducer handle. In vivo cardiac, abdominal, and obstetric B-scans with elevation focusing, as well as high speed C-scans, have been obtained with these 2-D arrays.

Two-dimensional arrays for medical ultrasound.

The design, fabrication and evaluation of two-dimensional transducer arrays are described for medical ultrasound imaging. A 4 x 32, 2.8 MHz array was developed to use new signal processing techniques for improved B-scan imaging including elevation focusing, phase correction and synthetic aperture imaging. Laboratory measurements from typical array elements showed 50 omega insertion loss of -56 dB, -6 dB fractional bandwidth of 43%, interelement crosstalk of -19 dB, and -6 dB pulse-echo angular response of 62 degrees. Simulations of pulse-echo beam plots have shown grating lobes 20 dB below the main lobe at +/- 7 degrees in the elevation direction. The complete 2-D array has been used for measurements of phase aberrations in breast, and the individual 32 element linear arrays have been used to obtain conventional B-scans. Several 16 x 16 arrays have also been developed for high speed volumetric imaging. These include 96 transmit elements and 32 receive channels. With a lambda/4 matching layer, laboratory measurements show 50 omega insertion loss of -72 dB, -6 dB fractional bandwidth of 63%, interelement crosstalk of -29 dB and -6 dB angular response of 25 degrees. Pulse-echo sensitivity was improved by 21 dB through the use of integrated circuit preamplifiers of high impedance mounted in the transducer handle. In vivo cardiac, abdominal, and obstetric B-scans with elevation focusing, as well as high speed C-scans, have been obtained with these 2-D arrays.

Does transducer selection affect aortic arch velocities?

The hypothesis tested was that transducers of different types and shapes would produce different peak and mean ascending aortic (AAo) velocities. Additionally, we sought to determine if mean and peak velocity recorded from the descending aorta (DAo) were similar to velocities in the AAo. Twenty-eight consecutive individuals who had normal hearts were studied. AAo velocities were measured with four traneducers including a nonimaging device that transmitted Doppler at right angies to the transducer handie, a 30-degree angled continuous wave transducer, an imaging transducer that transmitted Doppler in line with the transducer handle, and a second imaging transducer that sectored at 25 degrees to the transducer handle. DAo was studied with a standard in-line imaging transducer. Results showed that mean and peak AAo velocities recorded by transducers that transmitted off the axis of the transducer handle were similar, but the transducer that imaged along the transducer handle axis produced significantly lower peak and mean velocities. The problem that caused lower velocity for the on-axis transducer was inabillty to image the area immediately posterior to the sternum to permit alignment in the azimuthal dimension. The continuous wave transducer provided a wide spectral dispersion. Mean DAo velocity was simllar to mean AAo velocity, but variabillty was large.