Broadband Linear Array Research Articles

Broadband Linear Array With Photoconductive Weights

This letter presents the design, construction, and testing of an eight-element broadband array with photoconductive weights at each element. The photoconductive weights are activated by an IR LED and vary between on and off with a small reflection coefficient and small insertion loss. Test results for the elements and array are presented. A low sidelobe array pattern is demonstrated by tapering the illumination of the photoconductive weights.

Bedside Ultrasound for the Detection of Soft Tissue Foreign Bodies: A Cadaveric Study

The objective of this study was to evaluate the sensitivity and specificity of bedside ultrasound, as performed by emergency physicians with typical equipment, in detecting small, soft tissue foreign bodies, using a cadaveric model. This was a prospective study, using 6 unembalmed human cadavers and 6 ultrasound-credentialed, emergency medicine residency-trained physicians as sonographers. Incisions were made in 150 total sites of the extremities and each site was randomly assigned one of five groups: wood, metal, plastic, glass, or no foreign body. All foreign bodies were 2.5 mm 3 in total volume or less, no longer than 5 mm in any dimension, and inserted to a depth of up to 3 cm. Ultrasound was performed with a SonoSite TITAN ® (SonoSite, Inc., Bothell, WA) ultrasound system using a L38/10-5 broadband linear array transducer. Sonographers were blinded to the number, type, and location of foreign bodies. A total of 900 ultrasound examinations were recorded. Overall sensitivity of ultrasound for foreign body detection was 52.6% (95% confidence interval [CI] 48.9%–56.2%), and overall specificity was 47.2% (95% CI 39.9%–54.5%). Positive predictive value was 79.9% (95% CI 76.3%–83.5%), and negative predictive value was 20.0% (95% CI 16.2%–23.7%). Sensitivity for individual sonographers ranged from 40.8% to 72.3% (average 52.6% ± 13.3%), and specificity ranged from 30% to 66.7% (average 47.2% ± 15.1%). Inter-observer reliability was poor. In our model, bedside ultrasound performed by emergency physicians was neither sensitive nor specific for the presence of small soft tissue foreign bodies.

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.

Ultrasound Guided Dorsal Penile Nerve Block in Children

We describe a technique for using a portable ultrasound scanner (38 mm broadband (10-5 MHz) linear array transducer (Sonosite Titan SonoSite, Inc. 21919 30th Drive SE Bothell, WA.)) to guide dorsal penile nerve block in children under general anaesthesia. Real-time scanning is used to guide bilateral injections into the sub-pubic space, deep to Scarpa's fascia either side of the midline fundiform ligament. Scanning can confirm that the local anaesthetic has spread to contact the deep fascia on each side. A subcutaneous wheal of local anaesthetic along the penoscrotal junction completes the block.

Sonographic Features of Internal Hernia

The purpose of this series is to describe the sonographic findings in 4 patients with intestinal obstruction due to internal hernia. Four patients had clinical features of intestinal obstruction. Sonography was performed with broadband convex and linear array transducers in these patients. In all 4 patients, there were features of intestinal obstruction with a zone of transition between dilated and nondilated bowel. There was a cluster of crowded, compressed, and aperistaltic small-bowel loops, as if they were tightly packed within a sac, by the side of this zone in 3 patients. This appearance was due to obstruction of the afferent loop caused by compression. In the last patient, there were 2 loops of dilated bowel within a sac outlined by fluid due to obstruction of the efferent loop. All 4 patients had obstructed internal hernias at laparotomy. Sonographic features of internal hernia are described.

Interesting Cases

The objective of this study was to evaluate the sensitivity and specificity of bedside ultrasound, as performed by emergency physicians with typical equipment, in detecting small, soft tissue foreign bodies, using a cadaveric model. This was a prospective study, using 6 unembalmed human cadavers and 6 ultrasound-credentialed, emergency medicine residency-trained physicians as sonographers. Incisions were made in 150 total sites of the extremities and each site was randomly assigned one of five groups: wood, metal, plastic, glass, or no foreign body. All foreign bodies were 2.5 mm3 in total volume or less, no longer than 5 mm in any dimension, and inserted to a depth of up to 3 cm. Ultrasound was performed with a SonoSite TITAN® (SonoSite, Inc., Bothell, WA) ultrasound system using a L38/10-5 broadband linear array transducer. Sonographers were blinded to the number, type, and location of foreign bodies. A total of 900 ultrasound examinations were recorded. Overall sensitivity of ultrasound for foreign body detection was 52.6% (95% confidence interval [CI] 48.9%–56.2%), and overall specificity was 47.2% (95% CI 39.9%–54.5%). Positive predictive value was 79.9% (95% CI 76.3%–83.5%), and negative predictive value was 20.0% (95% CI 16.2%–23.7%). Sensitivity for individual sonographers ranged from 40.8% to 72.3% (average 52.6% ± 13.3%), and specificity ranged from 30% to 66.7% (average 47.2% ± 15.1%). Inter-observer reliability was poor. In our model, bedside ultrasound performed by emergency physicians was neither sensitive nor specific for the presence of small soft tissue foreign bodies.

Sonographic Diagnosis of Plantar Vein Thrombosis

The purpose of this series is to describe sonographic findings in 3 patients with plantar vein thrombosis. Three patients had sudden pain and swelling at the plantar side of the affected foot. Sonography of the plantar foot was performed with a broadband linear array working at 5 to 12 MHz. Gadolinium-enhanced magnetic resonance imaging was performed in 1 patient. Sonography showed enlarged incompressible plantar veins in all 3 cases. Magnetic resonance imaging confirmed venous thrombosis in 1 case. Pain and swelling at the plantar side of the foot can be caused by plantar vein thrombosis. This type of rare thrombosis can be diagnosed with sonography.

The value of colour Doppler imaging in assessing flow through ventriculo-peritoneal shunts.

So far, Doppler ultrasonography has had little application in paediatric neurosurgery. The incidental observation of normally invisible CSF flow from the peritoneal end of a ventriculo-peritoneal (V-P) shunt on colour Doppler during a conventional abdominal ultrasound examination in one of our patients suggested that colour Doppler imaging might be of potential interest. Using a 10-5 MHz broad-band linear array transducer, conventional 2D and Doppler (spectral and colour-coded) ultrasonography was performed in 17 patients with V-P shunts, who were aged 3 months to 12 years. In all, 20 examinations were performed, because 2 patients had repeat examinations before and after shunt revision. In 13 examinations (65%) CSF flow was identified through the shunt tube. Flow velocities between 5 and 7 cm/s were measured. No flow was seen in 7 examinations (35%), 3 of which (15%) were performed before revisions for a blocked shunt. Further in vitro studies with simulated shunt/ventricular system model demonstrated that although clear CSF is not ultrasonically visible, the presence of particulate matter, such as choroid plexus debris, can generate a satisfactory Doppler signal with the probe insonating over the length of the tubing. In the presence of clear CSF, turbulence generated at junction points of the shunt system or at the exit of the peritoneal tube can be visualised well with Doppler ultrasonography, presumably due to generation of microbubbles. The clinical implications for the management of shunt obstruction are discussed.

Acoustic surveys for marine mammals using a towed hydrophone array

For the purposes of identifying and locating marine mammals by their sounds, we designed a broadband linear array of hydrophones that is towed from a survey vessel. This array is a modification of the low‐frequency arrays currently used by the military and the geophysical industry. The array has been used during four studies: one offshore California, two in the eastern tropical Pacific, and one on a circumnavigation of Antarctica. Comparisons of visual and acoustic detections of marine mammals will be discussed. During one cruise as many as 32% of the marine mammals encountered were detected by the array, but not by observers. Factors affecting reception and detection of marine mammals will be discussed. We conclude that combining visual and acoustic surveys may produce more accurate species identifications and estimates of abundance for marine mammals.