Efficiency fitting for TDCR measurement data using polynomial approximation and the Newton-Raphson method.

A tritium radioactivity source was measured by triple-to-double coincidence ratio (TDCR) equipment of the National Metrology Institute of Japan (NMIJ), and measured data were fitted using polynomial approximation and the Newton-Raphson method, a technique whereby equations are solved numerically by successive approximations. The method used to obtain the activity minimizes the difference between statistically calculated data and experimental data. In the fitting, since calculated statistical efficiency and TDCR values are discrete, the calculated efficiencies are approximated by quadratic functions around experimental values and the Newton-Raphson method is used for convergence at the minimal difference between experimental data and calculated data. In this way, the activity of tritium was successfully obtained.

The use of colour Doppler imaging in the diagnosis of retinal detachment.

DESIGN: Prospective study. PURPOSE: To evaluate real-time duplex colour Doppler examination with colour and pulse Doppler ultrasonography (US) (colour Doppler imaging (CDI)) for detection of the retinal detachment from membranous structures in the posterior segment. MATERIALS AND METHODS: In 33 consecutive patients with ophthalmoscopically invisible eyes (34 eyes), CDI was performed to detect the presence or absence of retinal detachment. The diagnostic criterion for retinal detachment was whether or not spectral waveforms were detected in membranous structures with colour and pulse Doppler US. In all cases, the absence or presence of retinal detachment was confirmed by surgery. RESULTS: In 27 of 34 eyes, membranes and/or opacities were observed in the vitreous cavity with CDI. In 12 of these 27 eyes, blood flow in those structures was detected by CDI. In all of these 12 eyes, retinal detachment was confirmed at surgery, and in 14 of the 15 eyes in which blood flow was not detected by CDI, absence of retinal detachment was confirmed at surgery. When a diagnosis confirmed by surgery was used as the definitive finding, CDI had a sensitivity of 92.3%, specificity of 100%, positive predictive value of 100%, negative predictive value of 93.3%, and an accuracy in the detection of retinal detachment from membranes and/or opacities in the vitreous cavity of 96.3%. CONCLUSION: Real-time duplex colour Doppler examination with colour and pulse Doppler US (CDI) is a noninvasive method useful for the detection of retinal detachment from vitreous opacity and/or membrane in the posterior segment.