As Ultrasonic Doppler signal is very low in amplitude, it is necessary that signal-to-noise ratio of the Doppler signal be improved by use of transmission and reception circuit and transducer with higher sensitivity. Therefore, the transmission and reception system with single crystal was improved by, the authors. The principle of this system is as follows.
A bridge circuit, one element of which consists of the transducer with single crystal, is used for connecting three blocks, i. e., transmission circuit, transducer and reception circuit, and balanced against the transmitting signal, so that ultrasound can be simultaneously transmitted and received by a single crystal.
In actual use, however, the impedance of the transducer may fluctuate to unbalance the bridge circuit according to the change of acoustic load. As a result, the transmitting signal is fed to the input terminal of the receiving circuit, and the receiving amplifier may be saturated. Such an impedance fluctuation must be suppressed. Therefore, the following arrangement of transducer was newly employed. An acoustic coupler is set in between the crystal and acoustic load (skin, blood vessel, etc.), not including two surfaces parallel with each other in the pathway of ultrasound in order to prevent the standing wave. Therefore, the crystal is constantly loaded by the coupler, and the impedance of the transducer can become free from the load variation.
As compared with the transmission and reception system with dual crystal, this system was found to have improved the signal-to-noise ratio by 10 dB.

View full abstract

The multivariate analysis was applied to groups of blood dyscrasia : hereditery spherocytosis (HS) and autoimmune hemolytic anemia (AHA), to find out the index which reflects the dependency on the spleen of red blood cell destruction. In HS, almost all red cells are destroyed selectively in the spleen, so the splenectomy is the most effective treatment. But the cells of AHA are not always destroyed only in the spleen. According to whether or not the feature of its cell destruction is close to HS, the splenectomy should be indicated. After ⁵¹Cr injection to subjects, 4 observations were obtained : the blood destruction rate λ, RI accumulation rate in the spleen Δ (Sp/H), RI accumulation rate in the liver Δ (Liv/H), and the splenic volume per body weightSV. As the fifth value the ratio of Δ (Sp/H) to Δ (Liv/H) was introduced since this could be regarded as the approximation of the inde. To obtain more accurate index, the linear discriminant function and the quadratic function are chosen. With the set of these 5 variables both functions were carried out without variable transformation. And with another 2 sets, i. e., (λ, Δ (Sp/H), Δ (Liv/H), SV) and (λ, Δ (Sp/H) /Δ (Liv/H), SV), these procedures were appliedafter the logarithmic transformation.
The following are the results. 1) Δ (Sp/H) /Δ (Liv/H) which was introduced as the approximation index was not so effective. 2) Less subjects of AHA were discriinated from HS by the linear function than by the quadratic one. 3) The discriminant criteion on the non-transformed data seems to be less strict than on the logarithmic transformation. 4) The quadratic function gives more distinct discrimination than the linear function. 5) The contribution order of the variables are as follows ; SV, λ, Δ (Sp/H) Δ (Liv/H), Δ (Sp/H) and Δ (Liv/H). 6) Among 18 AHA subjects, one has features almost identical with HS, two have features close to HS, while the rest have a different features.

View full abstract

The flow-reaction-absorption system is one of the fundamental physiological systems and is characterized by the following reaction processes : a compound, usually a disaccharide or a dipeptide flowing into a pipe-structured reactor is hydrolyzed by a wall-bound enzyme and the resultant products are absorbed across the wall by an active transport mechanism. The small intestine and renal proximal tubule are the typical examples. Quantitative characteristics of its processes under dynamic conditions have not been well understood because of complex interactions of multiple factors which change along the length of the system.
In this paper, a digital simulation of this particular system has been attempted in order to understand characteristics of interactions of principal factors and effects of kinetic parameters of hydrolysis and transport on the intraluminal concentration profiles for the reacting and absorbed substances. The mathematical model introduced in the simulation is composed of two ordinary differential equations for intraluminal concentrations of the hydrolyzed substance and the product and one for the solvent flow rate. The former equations are accompanied with nonlinearities coming froin Michaelis-Menten kinetics involved in hydrolytic and transport processes. The model was applied to amphibian renal proximal tubule by assuming maltose as the substance to be hydrolyzed and glucose as the product. By using available data of geometry and kinetic parameters, the standard concentration profiles for both substances were obtained, then the effects of individual changes in values of important parameters were investigated.
It was found that the changes in kinetic parameters yielded characteristic changes in the concentration profiles while the 'flow rate little affected the concentration profiles. A distinct difference between the standard and experimentally observed pattern of the product concentration suggested that the actual biological system, has an additional special device (probably the microvillous structure) for efficient linkage between hydrolytic and transport processes.

View full abstract

The output (observations) of the tracer kinetic process is usually expressed by a sum of decaying exponemtials : q (t) =pΣi=1 A_i exp (-α_it). The compartmental analysis which is widely used in the tracer kinetic study is a method by which the pertinent parameters (A_i and α_i) as well as number of compartments (p) are determined. In this study the optimal time scale interval (τ) and sample size (m) in a definite set of observations in radio-isotope (RI) tracer kinetics were obtained to minimize the variances of the parameters (A_i and α_i), assuming the observations to be Poisson-distributed. The best unbiased estimators of variances of the parameters were obtained by the Fisher in formation and the Cramér-Rao inequality. Since the expectation value in the jth observation <nj> is represented by <nj> =∫tjtj-1 pΣi=1 A_i exp (-α_it) dt in RI study, the information matrix can be defined by A_i, α_i, τ and m.
Analysis of the effect of the sample size (m), the time scale interval (τ) and the number of exponentials (p) on the variance of A_i and α_i by numerical examples revealed the following results : (1) For a fixed sample size, there is an optimal time scale interval which increases with sample size. (2) For a fixed time scale interval, the variance of each parameter decreases withthe sample size, but it converges to a certain level for a large sample size. (3) The allowable limit on τ as the optimal time scale interval decreases with increase of the number of exponentials.
Application of this method to the dynamic study of cerebral circulation using ¹³³Xe revealed that 15-20 minutes of sampling period was necessary to estimate the pertinent parameters accurately.

View full abstract

In health-screening tests the normality of measured values are usually judged according to what is said to be the range of normal values. However, the accuracy of the judgment would be greater if the decision were based upon accumulated data of each subject. The justification for this test has been presented for actual data by comparing the variance of individual data and those of the whole group.
The main part of this paper deals with the problem of detecting any change of the population to which the measurement values of a subject are assumed to belong. The well-known t-test provides the answer to this problem under certain conditions.
In the present work the population mean is assumed to change with time. When the change is gradual instead of a jump, then the test may be deteriorated because of the violation of the conditions for the test. To examine the performance of the t-test in such a case, a model of a changing population mean is presented and the test is applied to it, yielding what can be considered as the average performance of the test.
Two methods (methods A and B) are examined. In method A, the n+1-th measurement value is compared with the mean of the past n values. Method B compares the mean of the recent two values with that of the past n-1 values. The results show how the number of independent “healthy” values and the rate of the change affect the performance.
The performance has been calculated using approximated formulas and the results of simulations using normal random variables show that the approximation is sufficient for roughly estimating the performance.

View full abstract