An automatic method of measuring inhibition of root growth of seedlings of Vicia faba following ultrasonic irradiation

A new method of monitoring the root growth of Vicia faba is described. This system comprises a double conductivity cell, each compartment accommodating one group of beans. The device is placed in a water-filled culture tank. The cell is connected to a high frequency bridge circuit, the out-of-phase signal from the bridge being extracted by a phase-sensitive detector, smoothed and amplified, and then passed to a pen recorder. The method can be used to continuously monitor either the growth of one set of beans in one compartment or the difference in growth rate between groups of beans. Traces are shown which illustrate the value of this approach.     

A digital technique for tracking moving interfaces

A digital technique is described for the tracking of variations in range of echoes reflected specularly from interfaces.     

A proposed standard target for ultrasound Doppler gain calibration

This communication describes a suggested target for the gain calibration of ultrasound Doppler systems used for blood flow measurement. The target consists of a fluid born suspension, treated in such a manner as to have a readily reproducible scattering cross section.     

High resolution electronic-linear-scanning ultrasonic diagnostic equipment.

Electronic linear-scanning ultrasonic diagnostic equipment so far has suffered from low resolution. In the study presented here, improvement in resolution was obtained by electronic focusing and improved image quality by small-angle deflection.Electronic focusing is a method obtaining a narrow ultrasonic beam by means of phase control. Small-angle deflection is a method to increase scanning line density by deflecting slightly the ultrasonic beam also by means of phase control and thus to obtain information existing between the successive scanning lines of a conventional linear scanning system. Both experimental investigation and clinical application have shown that these techniques are highly effective in increasing lateral resolution and image quality. It has been confirmed that the equipment is practical for routine use.     

Measurement of soft tissue motion using correlation between A-scans

The advent of real-time B-scanning has led to interest in the diagnostic value of the dynamic properties of soft tissue. Present ultrasonic techniques for investigating motion cannot measure the motion of homogeneous tissues. A technique has been developed which uses the correlation coefficient between A-scans to measure the amplitude and frequency of their motion, both in water tank experiments and in vivo. The success of the technique, which is digitally implemented, supports the validity of stochastic models for the acoustic structure of soft tissues. The motion pattern observed in vivo can be correlated with the arterial pressure pulse.     

ultrasonic array scanning of the kidney

An ultrasonic scanning system has been devised, utilizing an array of six plane transducers, each used as a separate transmitter-receiver. The transducers were arranged in a concave assembly so that their beams intersected at a point equidistant from each face. The array was mounted in a water-bath on a three-dimensional racking mechanism, so that it could be moved through a raster at various heights in the tank. In a fixed sequence, each individual transducer was excited, and the received ultrasonic echo amplitude information from the focus was selected by means of an electronic gate. The cartesian coordinates of the position of the array were also determined. Both sets of information were sampled, digitized and punched on to paper tape. A switching sequence was arranged so that eight successive characters on the paper tape represented the six echo amplitude data and the two positional data corresponding to a single point in the tank. The array was moved so that a two-dimensional matrix of points was interrogated.Experiments were performed to test the operating characteristics of the apparatus and to determine appropriate methods of signal processing and for the display of the information. It was found that the alignment of the ultrasonic beams was satisfactory and the data acquisition system was linear over a dynamic range approaching 40 dB. The apparatus was used to scan a simple model of wires and an isolated porcine kidney. Improved aximuthal resolution was achieved by combining the six amplitude data for each point. The product of these data seemed to be more useful than the sum. Contour mapping of received echo amplitude gave a satisfactorily wide dynamic range display.Possible future developments of the system are discussed.     

Use of a sphere radiometer to measure ultrasonic beam power

Making use of the theoretical work of Hasegawa and Yosioka, it is demonstrated that errors associated with either of the sound velocities in the spherical target can significantly shift the resonance dips in the variation of the radiation force function Y_p with ka. Without a knowledge of these acoustic parameters of the target, uncertainties may therefore occur in the computation of Y_p     

Determination of acoustic power outputs in the microwatt-milliwatt range

A system using an electrobalance for radiation pressure measurements has been developed capable of determining acoustic powers in the microwatt-milliwatt range. Low background “noise” levels are achieved by effective isolation of the balance from building vibrations and shielding the target from convection currents. The standard deviation for a power output of 1 mW is typically less than 1 percent.     

Depression of phagocytosis by ultrasound

Swiss mice insonated with a 2 megaHertz (MHz) wave at an energy level of 8.9-milliwatts/square centimeter (mW/cm²) applied over the liver had an impaired ability to clear injected colloidal carbon from their blood compared to untreated mice. Mice evaluated immediately after treatment had a depressed phagocytic index (K) and clearance half-time ($\text{T}\text{1}\text{2}$) but their phagocytic index corrected for liver and spleen weight (α) was normal. All three parameters deviated from normal if the clearance assay was conducted 48 or 72 hr after insonation, indicating a latency of the effect of ultrasound on the phagocytic system. The demonstration that peritoneal macrophages exposed in vivo to ultrasound also had depressed phagocytic abilities indicated that the reduced clearance of carbon from the blood of mice was not entirely due to damage to the liver.     

A fundamental interpretation of ultrasonic doppler velocimeters.

The basic Doppler equation is not entirely suitable when describing practical ultrasonic Doppler velocimeters. This article examines the operating principles of more useful devices such as continuous-wave and pulsed-Doppler systems. The analysis is based on intuitive concepts, illustrated by waveform and spectral plots and supported by short mathematical sequences. It is discovered that an uncertainty principle limits the velocity-spatial resolution product of any practical ultrasonic velocimeter.     

The differentiation of bile ducts and blood vessels using a pulsed Doppler system

Anechoic hepatic ducts are readily visualized by grey-scale ultrasound although differentiation of dilated bile ducts from portal veins can remain a problem. The supplementary use of a pulse-Doppler interfaced to a β-scanner as an aid to differentiation is investigated in a series of ten normal subjects and twenty patients presenting with suspected obstructive jaundice. The Doppler diagnoses were found to be in good agreement with the conclusions of more conventional methods such as endoscopic retrograde cholangio-pancreatography and liver biopsy.     

Advances in ultrasound mammography: remote focus arc scanning

A new form of automated scanning has been developed which overcomes geometric and amplitude distortion and physical scanning limitations, associated with simple arc scanning. In simple arc scanning, the transducer rotates about a point located behind the viewed object. This produces a dense concentration of scan lines around the point of rotation, resulting in a V-shaped type of geometric distortion.Remote focus arc scanning, reported in this paper, results in an arc scan which reduces this geometric distortion by substituting an imaginary focal point placed at infinity for a true point source of rotation. This is accomplished by simultaneous simple arc and sector scanning motions. This type of scan is required for ultrasound mammography of large breasts.     

Two-dimensional diffraction scanning of normal and cancerous human hepatic tissue in vitro

A technique and associated equipment are described which investigate the acoustic signals backscattered from small tissue volumes and interrogated over a solid angle of transmitter/receiver positions. This two-dimensional diffraction technique produces acoustic scatter maps termed, by us “interferograms”, which are analysed to determine their usefulness in discriminating between normal, freshly excised liver tissue and cancerous tissue within the intact organ. The “interferograms” are collected at three different narrow-band frequencies and have been used in investigating 26 normal liver and 13 liver tumour samples. The preliminary results indicate that this novel technique has a 97% success in discriminating normal liver from tumour, compared to an 87% success achieved by two observers when scoring conventional sector B-scan images of the same tissue regions.     

医学超声成像波束形成技术的演变

在过去几十年中,随着电子和计算机技术的发展,医学诊断超声成像技术发生了巨大变化,其临床应用价值大为提高.在组成超声成像系统的各个部分中,发射和接收超声波、采集检查部位数据的前端部分是制约整个系统性能的关键.本文从原理上介绍这方面的一些发展.     

Ultrasonic grey scale visualization of breast disease

Grey scale echography allows the display of the constituent tissues of the breast and provides a better method of differentiating between small solid and cystic lesions. Many pathological processes are associated with gross changes in their architectural structure as compared with the architectural structures of normal tissues. Grey scale echography is better able to display these changes than conventional techniques. In a series of 43 patients with suspected breast disease a correct interpretation was made in 90 per cent of cases, with malignancy being correctly diagnosed in 85 per cent.     

Evaluation of backscattering coefficients for excised human tissues: results,interpretation and associated measurements

Measurements are reported on the ultrasonic attenuation coefficient, the velocity of sound propagation and the differential scattering coefficient (for 180° scattering) for 3 types of freshly excised normal human tissues: liver, spleen and brain (white matter). The measurements are made as a continuous function of frequency in the range 0.7–7 MHz. The data for attenuation and scattering are consistent with a power law dependence on frequency though the latter are best described by a two-term fit. Comparison of the scattering data with theory suggests that two forms of tissue structure, with characteristic dimensions of approx. 1 and 0.02 mm, are predominantly responsible for scattering in the frequency range 0.5–5 MHz. The absolute value of backscattering for freshly excised human liver tissue at 1 MHz is 3.5 × 10^?4cm^?1Sr^?1 rising to 9.0 × 10^?4cm^?1Sr^?1 at 3 MHz. Extrapolation to total scattering suggests that the contribution of scattering to attenuation varies from approx. 2% at 1 MHz to 5.4% at 3 MHz.     

Assessment of gestational age in the first trimester of pregnancy by maximum fetal diameter

A method using ultrasound to estimate fetal gestational age between the sixth and fourteenth week of pregnancy is described. The maximum fetal diameter is measured by a modification of the technique developed by Robinson (1973, 1975) to determine crown-rump length. Correlation of values for maximum fetal diameter with subsequent estimation of gestational age by ultrasound at adjudged 24 weeks, by X-ray at adjudged 37 weeks and also with the actual date of delivery, confirmed the accuracy for clinical purposes of this simplified method.     

Sonoluminescence, in water and in human blood plasma, generated using ultrasonic therapy equipment

Sonoluminescence in a liquid indicates both cavitation and free radical formation. This experimental study showed that it can be generated in both water and blood plasma using ultrasound at therapeutic intensities (less than 2W cm⁻², spatial average) and frequencies (0.75 and 1.5 MHz). Pulsing the ultrasound raised the intensity threshold for sonoluminescence. Recordings of acoustic emission from the liquid (for 0.75 MHz continuous insonation) showed that sonoluminescence was accompanied by the emission of ‘broad-band’ noise. The applicability of these results to tissue insonation, and the implications for ultrasound therapy, are discussed.     

声辐射力弹性成像:弹性成像的新发展

弹性成像作为一种重要的组织定征手段在过去20年里成为研究热点。传统的静态/准静态弹性成像难以从体外对体内通过机械方法进行有效施压,近年来研究者专注于新的远程"触诊"手段,即声辐射力弹性成像。本文对三种主要声辐射力弹性成像方法,即谐波运动成像、脉冲声辐射力成像和剪切波弹性成像的研究进行综述。     

超声靶向微泡击破介导基因转染或药物传输的研究进展

超声靶向微泡击破(UTMD)是一种新兴的靶向给药及基因转运方法,以超声微泡造影剂作为药物或基因转送的载体,主要作用机制是声孔作用,即胞膜上形成的瞬时孔.超声辐照于靶组织或靶器官,靶部位载基因或载药微泡后靶向释放出基因和药物,提高药物和基因转染率.UTMD为现代的基因治疗提供了一种新的、安全的、非病毒性的转运手段.本文对UTMD技术的作用机制、应用进展及其影响因素进行综述.