Spike-triggered Covariance Research Articles

Accuracy of abnormal karyotypes after the analysis of both short- and long-term culture of chorionic villi

We report in detail the cytogenetic results of 1838 consecutive chorionic villus samples with the availability of both short-term culture (STC-villi) and long-term culture (LTC-villi) preparations in 1561 cases (84.9%). A high degree of laboratory success (99.5%) and diagnostic accuracy (99.8%) was observed; in four cases of low mosaicism, all four associated with the final birth of a normal child, a small risk of uncertainty was accepted. The combined analysis of STC- and LTC-villi reduced follow-up amniocenteses by one-third in comparison with the analysis of STC-villi alone. We believe that the desired level of quality and accuracy of prenatal cytogenetics in chorionic villi can only be achieved when both STC- and LTC-villi are available. We conclude that CVS might then be the mode of prenatal diagnosis of first choice in pregnancies with a high (cytogenetic) risk.

Description of a computerized system for analysis of reverberation time, STC and IIC

The computer of an FFT system was interfaced to a 13‐octave band real‐time analyzer to reduce analysis time of tape recorded data as well as increase accuracy. Some of the programs developed for this system are described. These include a reverberation‐time analysis program which allows time averaging of decays for each 13‐octave band from 100 Hz to 5 kHz simultaneously, and displays the decays on a CRT. An operator can then select for each 13‐octave band any portion of the decay, by means of cursors, on which a straight‐line, least‐squares curve fit is performed to determine the reverberation time. The time‐averaged decays can be plotted on a digital plotter in order to examine double slopes or other decay characteristics in detail. Other programs developed include those for determining the space‐average SPL in a room from a moving microphone, the results of which are stored in a file on magnetic disk. The stored spectra, reverberation times and appropriate room dimensions are then used by other programs to determine transmission loss and STC or normalized SPL and IIC. These values along with STC or IIC contours can be plotted directly with appropriate labels for inclusion in a report.