Cystic thyroid lesions in children

BACKGROUND/PURPOSE: Cystic lesions of the thyroid encompass a wide and heterogeneous group of disease states in children, ranging from benign purely cystic entities to malignant tumors. The purpose of this study was to study both the presentation and management of cystic thyroid lesions in the pediatric population. METHODS: A retrospective review of all thyroid masses presenting between 1978 and 1996 and found to be purely or partially cystic on ultrasound examination was conducted, looking at presentation, family history, laboratory values, ultrasound scan and radionuclide imaging, and pathological and cytological evaluation. RESULTS: Twenty-four patients (19 girls, 5 boys) aged 6 to 18 years received the diagnosis of cystic lesions of the thyroid. Of these, 23 presented with painless neck masses, 21 were clinically euthyroid, only one had a single abnormal thyroid function test, only two had mildly positive antithyroid antibody test results, and nearly 30% had a positive family history of thyroid disease. Ultrasonography showed pure cysts in five patients and mixed solid cystic lesions in 19 patients. On scintiscan, six lesions were hot, 13 were cold, three showed normal uptake, and two were mixed. Treatment included either observation, aspiration, cyst sclerosis, surgery, or combinations thereof. Pathological and cytological results included follicular adenoma (n = 9), cystic degeneration (n = 6), multinodular goiter (n = 4), carcinoma (n = 2), branchial cleft cyst (n = 1), and undetermined (n = 2). CONCLUSIONS: Thyroid cysts are often thought to represent benign degenerative disease. Our study, which is the first in the literature to specifically address thyroid cysts in children, shows that ultrasound scan is useful in evaluating thyroid masses, whereas laboratory and radionuclide are of less value, and that single lesions of mixed echogeneity are likely to represent neoplasms, a significant percentage of which are malignant.     

A new criterion for linear 2-port stability using a singlegeometrically derived parameter

A stability parameter, μ(S), is defined for linear two-port circuits using a geometrical approach. It is shown that μ>1 alone is necessary and sufficient for a circuit to be unconditionally stable. This single parameter can replace the dual Rollet (K>1) and auxiliary conditions for determining unconditional stability. The parameters K and μ are compared by discussing their implications in terms of mapping circles     

Infant mortality review as a vehicle for quality improvement in a local health department

BACKGROUND: Many communities across the United States have established fetal and infant mortality review (FIMR) programs as a way of gaining insight into the causes of such deaths and of devising and implementing ways to improve the health of pregnant women and their infants. IMR PROCESS: The IMR process in the Jefferson County Department of Health in Birmingham, Alabama, evolved in a somewhat different fashion than that in other communities. A technical review team reviews all the infant deaths in the county, with particular attention to each woman's pregnancy history. A community review team reviews composite cases that illustrate some particular problem that might lead to infant mortality, such as teenage pregnancy or short intervals between pregnancies. This team provides insights into cultural patterns and a community perspective on the problems. Recommendations from the two teams are acted on by the health department, with the assistance of other agencies as needed. IMPACT OF THE IMR PROCESS: The IMR process has been used to increase community agency participation in health department activities, improve health department procedures, increase health department staff acceptance of a new and controversial program (Healthy Start), and offer services to women who need them. CONCLUSIONS: IMR has become a mechanism for CQI in the health department, embodying many of the principles of CQI, including the use of teams, focus on a team mission, and examination of processes, not individuals. The program offers a model of how to reduce rates of fetal and infant mortality.     

10-Gb/s upgrade of bidirectional CWDM systems using electronic equalization and FEC

We discuss options for upgrading coarse wavelength-division multiplexed (CWDM) optical access links over standard single-mode fiber (SSMF) by increasing per-channel data rates from 2.5 to 10 Gb/s. We identify electronic equalization and forward error correction (FEC) as the enabling technologies to overcome the dispersion limit of SSMF. In addition, we show how FEC enhances the tolerance to in-band crosstalk, and paves the way toward fully bidirectional CWDM transmission. Due to the lack of CWDM sources rated for 10-Gb/s operation, we demonstrate full-spectrum (1310 to 1610 nm) 10-Gb/s CWDM transmission over standard-dispersion fiber using uncooled, directly modulated lasers specified for 2.5 Gb/s. All 16 CWDM channels could be transmitted over more than 40 km, yielding a capacity-times-distance product of 6.4 Tb/s/km. The longest transmission distance (80 km) was achieved at 1610 nm, equivalent to 1600 ps/nm of chromatic dispersion.     

High-speed data and pulse-carver alignment in dual Mach-Zehnder modulator optical transmitters using microwave signal processing

A novel approach is presented for aligning the pulse carver and data modulator in a dual Mach-Zehnder (MZ) modulator optical transmitter. This technique relies solely on the photodiode detected microwave power spectrum of the transmitted optical signal. Experimental results are presented that illustrate the spectral property to be exploited and two proposed techniques for designing a low cost automated carver and modulator alignment system. A mathematical explanation for the spectral phenomenon is presented and shown to agree quite well with measurement and simulation results.     

RZ-DPSK transmission using a 42.7-Gb/s integrated balanced optical front end with record sensitivity

We have demonstrated a record sensitivity of -37.0 dBm (38 photons/bit) for a BER of 10/sup -9/ at 42.7-Gb/s using an integrated balanced optical front end. Results were obtained using optical preamplification of RZ-DPSK modulation and an external delay-interferometer. The OSNR requirement was measured to be 16.9 dB in a 0.1-nm bandwidth. The impact of polarization-mode dispersion (PMD) and chromatic dispersion on the optical front end performance has been measured. Performance for enhanced forward error correction has been projected based on 10/sup -3/ BER performance.     

Low-voltage high-speed travelling wave InGaAsP-InP phase modulator

A high-speed low-drive-voltage travelling wave electrodes InGaAsP-InP phase modulator operated at 1.55 /spl mu/m is demonstrated. The modulator is fabricated using a multiple quantum-well optical waveguide with an on chip integrated termination resistor. A small signal bandwidth of 35 GHz and a V/spl pi/ of 1.8 V has been demonstrated.     

A 107-Gbit/s Optoelectronic Receiver Utilizing Hybrid Integration of a Photodetector and Electronic Demultiplexer

A novel 107-Gbit/s optoelectronic receiver has been designed using hybrid integration of a photodiode and electronic demultiplexer. Using an ETDM transmitter, we achieve the lowest reported required OSNR for 107-Gbit/s CSRZ-OOK, 21 dB for 10^-3 BER and a 2³¹-1pattern length. Design methodology and performance data are presented.     

High-speed electrical backplane transmission using duobinary signaling

High-speed electrical data transmission through low-cost backplanes is a particularly challenging problem. We present for the first time a very effective approach that uses the concept of duobinary signaling to accomplish this task. Using a finite-impulse-response filter, we are able to compensate for the phase and amplitude response of the backplane such that the resulting frequency response of the channel is that of an ideal duobinary filter. At the output of the backplane, we use an innovative pseudodigital circuit to convert the electrical duobinary to binary. For 10-Gb/s data transmission, we demonstrate a bit error rate <10/sup -13/ through electrical backplane traces up to 34 in in length on FR4. A full discussion of the concept, system architecture, and measured results are presented. Analysis is presented that compares and contrasts this approach to PAM-4 and standard nonreturn-to-zero signaling.