Biomedical subjects

C D Emery

Publications and source records attributed to C D Emery.

4 recordsLinked to original sources

PubMed1998

Ultrasonic imaging using optoelectronic transmitters.

Conventional ultrasound scanners utilize electronic transmitters and receivers at the scanner with a separate coaxial cable connected to each transducer element in the handle. The number of transducer elements determines the size and weight of the transducer cable assembly that connects the imaging array to the scanner. 2-D arrays that allow new imaging modalities to be introduced significantly increase the channel count making the transducer cable assembly more difficult to handle. Therefore, reducing the size and increasing the flexibility of the transducer cable assembly is a concern. Fiber optics can be used to transmit signals optically and has distinct advantages over standard coaxial cable to increase flexibility and decrease the weight of the transducer cable for larger channel numbers. The use of fiber optics to connect the array and the scanner entails the use of optoelectronics such as detectors and laser diodes to send and receive signals. In transmit, optoelectronics would have to be designed to produce high-voltage wide-bandwidth pulses across the transducer element. In this paper, we describe a 48 channel ultrasound system having 16 optoelectronic transmitters and 32 conventional electronic receivers. We investigated both silicon avalanche photodiodes (APD's) and GaAs lateral photoconductive semiconductor switches (PCSS's) for producing the transmit pulses. A Siemens SI-1200 scanner and a 2.25 MHz linear array were used to compare the optoelectronic system to a conventional electronic transmit system. Transmit signal results and images in tissue mimicking of cysts and tumors are provided for comparison.

Fiber Optic Technology↗

PubMed1997

Improved signal-to-noise ratio in hybrid 2-D arrays: experimental confirmation.

2-D array transducers have shown significant promise for medical ultrasound over conventional linear arrays, at the cost of increasing the number of channels, difficulty of fabrication and array element impedance. The increase in element impedance reduces the power coupled to a 2-D array element from a conventional 50 omega source in transmit mode. If the array is sparse, which is typical of 2-D arrays, then the net power coupled into the front acoustic load is reduced when compared to a fully sampled aperture. Furthermore, the received signal-to-noise ratio (SNR), when measured through a nonideal amplifier, is degraded because the high impedance 2-D array transducer element cannot efficiently drive the coaxial cable. The reduction in transmit sensitivity and received SNR can be circumvented with the application of multilayer piezoelectric elements. The improvement in transmit occurs because the transducer impedance is better matched to the impedance of the source. In receive, multilayer elements allow more of the open circuit received voltage to fall across the input of the high impedance preamplifier. In this case, the same number of layers are used in transmit and receive. Recently, it has been suggested that separate optimization of the transmit channel and receive channel (a hybrid array) would further improve the pulse-echo SNR. In this paper, we fabricated and tested a hybrid array operating at 1 MHz using a multilayer transmit element and single layer receive element. A 7 omega transmitter and high impedance preamplifier were placed adjacent to the transmit and receive elements within the transducer assembly. The hybrid pulse-echo SNR improved by 26.4 dB over the conventional array. The experimental result showed good agreement with the KLM model. Furthermore, KLM simulations showed that as the operating frequency of the array increases, the overall improvement over the conventional array increases. For example, a 1.5-D array operating at 2 M Hz had an improvement of 30 dB whereas a 7.5 M Hz 1.5-D array showed an increase of approximately 38 dB. The separate optimization of the transmit and receive channel for 2-D arrays showed even greater improvement than for 1.5-D arrays. For example, a 2 MHz 2-D array had an improvement of over 44 dB.

Humans↗

PubMed1994

Case report 865. Bacillary angiomatosis.

A case of bacillary angiomatosis was presented, characterized by subcutaneous lesions, systemic symptoms, and impressive periostitis which initially masked a small cortical lytic lesion. Review of the reported cases suggests that a diagnosis of bacillary angiomatosis should be strongly considered when periostitis is identified in an AIDS patient with skin lesions. Additionally, deep surgical biopsy of the skin lesion to include the subcutaneous tissue should be performed to confirm the diagnosis if the initial punch biopsies are unrevealing.

AIDS-Related Opportunistic Infections↗

PubMed1986

Pharyngeal Kaposi's sarcoma in patients with AIDS.

The radiographic appearance of gastrointestinal Kaposi's sarcoma in patients with AIDS has been described previously, but little attention has been paid to pharyngeal involvement. This study compared the radiographic findings of pharyngeal Kaposi's sarcoma in eight patients with AIDS and dysphagia to those of visual inspection by laryngoscopy or bronchoscopy. Barium pharyngography (six patients) demonstrated nodular lesions without ulceration, ranging in extent from a single nodule to extensive confluent disease. CT (two patients) showed nodular or polypoid intraluminal protrusions, distortion of valleculae and pyriform sinuses, infiltration of deep-tissue planes, and adenopathy. A 4-mm nodular lesion was not seen on pharyngography. Radiographic evaluation provided supplemental information in six patients, especially regarding inferior extent of disease in four whose bulky lesions precluded adequate visual assessment. CT aided in defining deep-tissue-plane involvement and extent of nodal disease. It is concluded that barium pharyngography and CT are useful in the diagnostic evaluation of possible Kaposi's sarcoma in patients with AIDS and dysphagia.

Acquired Immunodeficiency Syndrome↗