Ultrasonic Imaging Device Research Articles

High frequency ultrasonic scattering by biological tissues

High frequency (HF) diagnostic ultrasonic imaging devices at frequencies higher than 20 MHz have found applications in ophthalmology, dermatology, and vascular surgery. To be able to interpret these images and to further the development of these devices, a better understanding of ultrasonic scattering in biological tissues such as blood, liver, myocardium in the high frequency range is crucial. This work has previously been hampered by the lack of suitable transducers. With the availability of HF transducers going to 90 MHz, HF attenuation and backscatter experiments have been made on porcine red blood cell (RBC) suspensions, for which much data on attenuation and backscatter can be found in the literature in the lower frequency range for frequencies, from 30 to 90 MHz and on bovine tissues for frequencies from 10 to 30 MHz using a modified substitution method that allow the utilization of focused transducers. These results will be reviewed in this talk along with relevant theoretical models that could be applied to interpreting them. The relevance of the parameter that has been frequently used in the biomedical ultrasound literature to describe backscattering, the backscattering coefficient, will be critically examined.

High frequency backscatter and attenuation measurements of porcine red blood cell suspensions between 30 and 90 MHz

There are now diagnostic ultrasonic imaging devices that operate at very high frequencies (VHF) of 20 MHz and beyond for clinical applications in ophthalmology, dermatology, and vascular surgery. To be able to better interpret these images and to further the development of these devices, knowledge of ultrasonic attenuation and scattering of biological tissues, such as blood, in this high-frequency range is crucial. VHF experiments were performed on porcine red blood cell (RBC) suspensions, which have been used in ultrasound experiments by many investigators but in a lower frequency range. Attenuation and backscatter from various hematocrit levels (6%, 10%, 15%, 20%, 25%, 30%) from 30 to 90 MHz were measured using focused transducers. The dependence of the attenuation coefficient from all suspensions followed linearly while the backscatter coefficient for low hematocrit suspensions was found to be a maximum between 10% and 15%. The higher hematocrits showed a decrease in their frequency dependence, possibly no longer indicating Rayleigh scattering since the wavelength is not much larger than the size of a porcine RBC. These results as well as the frequency limits of these type of scattering experiments will be discussed.

High-frequency backscatter and attenuation measurements of selected bovine tissues between 10 and 30 MHz

There are now diagnostic ultrasonic imaging devices that operate at very high frequencies (VHF) of 20 MHz and beyond for clinical applications in ophthalmology, dermatology, vascular surgery, endoluminal imaging and small animal imaging. To be able to better interpret these images and to further the development of these devices, knowledge of ultrasonic attenuation and scattering of biological tissues in this frequency range is crucial. Attenuation and backscatter coefficients (BSCs) of bovine tissues in the frequency range of 10 to 30 MHz were measured, respectively, using a standard substitution method for attenuation measurements and a modified narrow-band substitution method for scattering measurements. A modified substitution method for scattering measurements has to be used at high frequencies because unfocused transducers due to their decreased sensitivity cannot be used in the simple substitution method. In the modified method, the flat reflector is substituted by a particulate reference medium whose BSC is well-known and documented; in this case, a red cell suspension. In this paper, experimental results on BSC and attenuation coefficient measured between 10 and 30 MHz are reported. The frequency dependence of backscatter of the selected bovine tissues ranges from 2.4 to 3.5, whereas attenuation is observed to be still approximately linearly proportional to frequency. The BSC measured with the modified method is in good agreement with those obtained with the standard method between 10 and 20 MHz.

Echogenicity of fetal lung and liver quantified by the grey-level histogram width

Grey-level histogram width (GLHW) values of fetal lung and liver were studied in 52 healthy fetuses in 24 to 38 weeks of pregnancy, comparing them to the mean grey level (MGL), grey-level standard deviation (GLSD) and the coefficient of variation (GLCV). Fetal lung GLHW was larger in 30–38 weeks than at 24–29 weeks, but there was no change in liver GLHW. GLHW was smaller in fetal lung than in the liver in 24–29 weeks, with no difference in 30–38 weeks. The lung/liver GLHW ratios were less than 1 in 24–29 weeks, but they were 1 or more in 30–35 weeks. Both MGL of fetal lung and liver showed linear increases during pregnancy, but no difference was found between the two. Fetal lung GLSD tended to decrease during pregnancy. The GLCV values of fetal lung and liver decreased during pregnancy, and differed between 24–29 weeks and 30–38 weeks, whereas there was no difference between fetal lung and liver. The correlation coefficients of GLHW and MGL of fetal lung and liver to the weeks of pregnancy were moderate, and the coefficients of GLSD and GLCV to the weeks of pregnancy were small. In conclusion, quantitatively measured echogenicity of fetal lung increased in 30 or more weeks of pregnancy, and suggested antepartum changes of fetal lung tissue. The GLHW is reliable, because it was reproducible in various gain settings of various ultrasonic imaging devices. The MGL, GLSD and GLCV are less reliable, because the grey level varied by the gain changes among various machines.

Validation of an ultrasound scanner for determing urinary volumes in surgical patients and volunteers.

As bladder distension related to anaesthesia puts patients at risk for permanent dysfunction, peri-operative determination of bladder volume is of great importance. The aim of this study is to validate an ultrasonic imaging device for determing bladder urine volume. To evaluate a broad volume range, ultrasonically scanned volumes were compared to true urinary volumes both in surgical patients and in volunteers. After institutional approval and informed consent 60 healthy volunteers were asked not to void for as long as possible. After ultrasound measurements (BladderScan BVI 2500, Diagnostic Ultrasound, Redmond WA, U.S.A.) they voided and true urinary volumes were measured. Fifty surgical patients scheduled for procedures requiring urinary catheterisation were studied. Pre- and post-induction of anaesthesia ultrasound measurements were recorded, followed by urinary catheterisation and measurement of true urinary volume. Urine volumes were compared using Student t-tests and Wilcoxon Rank Tests (p < 0.05). For validation linear regression was used together with Bland-Altman analyses. Ultrasonic scanning underestimated the true urine volume by about 7% over the whole volume range (17 ml to 970 ml). Underestimation was larger in females than in males (p < 0.02). R2 values for correlation of measured and scanned urinary volumes ranged between 0.92 and 0.95. Bland and Altman analyses showed a bias of 31 ml in volunteers and of 19 ml in patients and a precision of 110 ml and 80 ml, respectively. The ultrasonic imaging device can be used peri-operatively to establish bladder volume, taking into account the 7% underestimation of the bladder volume.

Clinical feasibility of 0.018-inch intravascular ultrasound imaging device

Objectives Intravascular ultrasound imaging (IVUS) is limited by the size of the imaging catheter. To facilitate imaging before and during interventions, a 30-MHz ultrasonic imaging device was developed that is the same dimension as a 0.018-inch guide wire. The purpose of this study was to evaluate the clinical feasibility of this device. Methods and Results The imaging core was tested in 8 patients with the use of a monorail guiding sheath that was advanced through a 7F catheter. In addition, after coronary interventions, the standard guide wire was removed, the imaging core was placed inside a compatible balloon, and imaging was performed. In 4 patients, imaging was also performed with a standard 3.2F IVUS catheter. The lumen-plaque interface and the media-plaque interface were clearly visualized in all patients. There was no detectable loss in image quality between the new imaging device and the larger IVUS catheter, and measurements of lumen cross-sectional area were not statistically different. Conclusions Improvements in manufacturing technology have permitted the development of a mechanically rotating ultrasound imaging core 0.018 inches in diameter. It is compatible with current balloon catheters without degradation of image quality. (Am Heart J 1998;136:1017-20.)

Simulation of the effects of thermal turbulence on beamforming and time reversal techniques using Gaussian beam summation and Fourier modes superposition techniques

In-service inspection of Fast Breeder Reactors will require submerged ultrasonic imaging devices. For this purpose, the CEA (French atomic commission) is developing an orthogonal imaging system, based on beamforming applied to two linear arrays. In order to evaluate the performance of this technique for realistic physical conditions, one must take into account the possible effects of weak thermal turbulence on the propagation and focusing of ultrasound. To achieve this study, a numerical model has been implemented. It is based on the Fourier modes superposition method to generate independent realizations of turbulent fields and on the Gaussian beam summation method to calculate the associated acoustic pressure fields induced by point sources. First, the model has been used to show the aberrations that are created in the focusing of a multielement transducer. Second, the model has been used to verify the efficiency of the time reversal technique for the correction of these aberrations, in the case of slow temporal evolutions of the turbulence.

Ultrasonic ventriculostomy stylet.

I describe my design for a ventriculostomy stylet fitted with a phase array ultrasonic imaging device in its tip. Theoretically, this would allow identification of the ventricles and their exact location at the bedside, without the need for expensive stereotactic equipment. A device such as this could potentially facilitate the placement of ventriculostomy catheters in patients with small ventricles, and it could even contribute to the education of neurosurgery residents. At present, a prototype of the device is being manufactured.

Color Measurering Principles and Color Appearance Ultrasonic Imaging Device in Medical Diagnosis

Color Measurering Principles and Color Appearance Ultrasonic Imaging Device in Medical Diagnosis

Ultrasonic Imaging Device in Medical Diganosis-Current Status and Trend-

Ultrasonic Imaging Device in Medical Diganosis-Current Status and Trend-

5027659 Ultrasonic imaging device in which electroacoustic transducers are disposed on a convex probe

5027659 Ultrasonic imaging device in which electroacoustic transducers are disposed on a convex probe

Intravascular ultrasound and vascular intervention.

An intravascular ultrasonic imaging device (40 MHz) was used to obtain in vitro ultrasonic images and matching histologic cross-sections, derived from human vascular specimens. The feasibility of assessing vessel wall morphology as well as the ability to accurately document plaque thickness was determined. Based on the echogenicity of the arterial media, intravascular ultrasound could distinguish muscular arteries from elastic arteries, veins, and bypass grafts. The hypoechoic media only present in the muscular type of artery proved to be an essential landmark to document superimposed atherosclerosis. Plaque thickness calculated in these arteries showed close relationship with the corresponding histologic cross-section. Using real-time in vivo intravascular imaging (30 MHz), the morphology of the vessels interrogated was studied. The dynamic change of the arterial wall, as well as the outcome after intervention, is discussed.

Ultrasonic imaging device

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Intravascular ultrasonic imaging: Histologic and echographic correlation

The feasibility of assessing arterial wall characteristics with an intravascular 40 MHz ultrasonic imaging device was determined in vitro. Ten autopsy specimens of human arteries, with and without atherosclerosis, were studied. A close relationship was observed between the histologic section and the corresponding ultrasonic cross-section with regard to the location, maximum plaque thickness and extent of the atherosclerotic lesion along the circumference of the vessel wall. Based on echogenicity of the atherosclerotic lesion, ultrasound could distinguish four basic types of atherosclerotic plaque components: 1. hypoechoic: a reflection of lipid deposits; 2. soft echoes: reflective of fibromuscular tissue; 3. bright echoes: representative of fibrous tissue; 4. bright echoes with shadowing behind the lesion: representative of calcium deposits. It is anticipated that development of such a catheter-tip imaging system combined with recanalisation methods will be of immense benefit for the precise localisation and identification of vessel wall pathology, precise positioning of a recanalisation instrument (laser device, atherectomy catheter) and subsequent use of this recanalisation procedure and for assessing the effect of recanalisation.

Resolution and display requirements for ultrasound Doppler/evaluation of the heart in children, infants and the unborn Human fetus

Technical considerations and the instrumentation used for pediatric two-dimensional echocardiography and Doppler examination are reviewed. The configurations of sector scanners, the function of the mechanical versus phased array systems and considerations related to lateral, axial and azimuthal resolution requirements are discussed. The performance and requirements for echocardiographic cardiographic scan converters and the requirements for pediatric display are reviewed. Methods of performing quantitative Doppler echocardiography are discussed because this technique provides new and important types of information for the evaluation of congenital heart disease. Considerations of Doppler velocity, Doppler spatial resolution and Doppler display requirements are presented. Characteristics of ultrasonic imaging devices for use in fetal echocardiography and fetal Doppler study are reviewed, and a brief overview of techniques for the extraction of information about the nature of ultrasound scatterers (that is, tissue signature) is presented. It is the purpose of this technically oriented discussion to present the capabilities, trade-offs and needs for future development relevant to pediatric echocardiography in 1983.

Explososcan: a parallel processing technique for high speed ultrasound imaging with linear phased arrays.

The data acquisition rate in medical ultrasonic imaging devices is limited by the acoustic propagation velocity in the tissues. Typically in such machines the image lines are produced sequentially one line per transmitted pulse. A parallel processing scheme has been implemented which enables the data acquisition rate to increase by a factor of four through the simultaneous acquisition of four B-mode image lines from each individual broadened transmit pulse. The higher data rate can be used to increase the image frame rate to produce independent images that can be averaged in the image frame to reduce noise, or to produce a conventional image at standard video frame rates while reducing patient exposure. Alternatively, the field of view can be increased over that of a normal scan without sacrificing frame rate. These advantages are achieved with little reduction in the measured resolution. The design and performance of this device are described. A sample in vivo image is included.

Ultrasonic diagnostic instruments.

The underlying physical principles and current limitations of diagnostic ultrasonic instruments are reviewed. Recently developed ultrasonic imaging devices using pulsed-reflected ultrasound are discussed in detail. These instruments transmit short trains of 1.5- to 10-megahertz sound. Echoes reflected from tissue are converted to electrical signals, which are presented on a display device to outline the contour of tissues and organs within the body. The physical resolution of the system is dependent on several design factors in addition to the transmitted sound frequencies. A resolution volume of approximately 1.5 by 3 by 4 millimeters is achieved optimally with commercially available systems operating at 2.25 megahertz. The various instrument designs are described in the context of clinical usage. Because the sound is diffracted, refracted, and reflected, tghe imaging considerations are different from those of x-ray imaging. Diagnostic devices based on the Doppler principle are distinguished from pulsed-reflected ultrasonic instruments.

Electrical coupling effects in an ultrasonic transducer array

Ultrasonic imaging devices often use transducer arrays for sampling the incoming acoustic field and converting it into electrical signals. After some convenient processing (amplification, dephasing, summing, etc), the electrical signals are used to modulate the brightness of a cathode ray tube (crt) monitor on which the ultrasonic image becomes visible. The quality of the imaging apparatus depends critically on the transducer array design and implementation. Each individual transducer would, ideally, produce an electrical signal related exclusively to the ultrasonic field arriving at its surface; the reciprocal would also be true for transmission. In all practical cases, however, numerous effects lead to some coupling between nearby transducers, especially for very narrow transducers. The subsequent perturbations may be described as a narrowing of the radiation (or reception) pattern of the individual transducers, with respect to the theoretical predictions. To understand the mechanism for these couplings and to minimize them, their possible origins have been systematically studied. One of the most important sources of coupling is electrical leakage, which is reported here. Since no simple analytical calculation can be performed, diagrams have been established that enable evaluation of the electrical coupling against the dimensional characteristics of the array. Some means for reducing this coupling are suggested and comparative experimental results are given.

Medical ultrasonic imaging: An overview of principles and instrumentation

Recent advances in electronics and digital processing techniques have significantly improved conventional ultrasonic imaging systems and allowed the development of new and sophisticated scanning methods. As a result, ultrasonic imaging devices have become an important modality for the clinical radiologist, complimenting the images obtained from X-ray and nuclear cameras. A particular advantage of ultrasonic waves is that they are nonionizing, thus presenting less risk to both patient and examiner. This paper presents some of the basic principles of ultrasonic propagation in tissue and how those principles impact the design of imaging devices. The characteristics of both the B- scan and C-scan techniques are described along with a summary of various scan formats that are currently available. Examples of B-scan and C-scan instruments are presented along with their relative advantages, limitations, and current usage;representative images are presented whenever possible. This paper concludes with a description of some new research developments in this rapidly emerging technology.

Ultrasonic real time imaging with a hand-held-scanner Part II—Initial clinical experience

The initial clinical results and potential applications of a miniaturized, battery powered and hand-held ultrasonic imaging device are described. Tests performed in 60 patients on the general cardiology, obstetrics/gynaecology and internal medicine wards demonstrated that good imaging quality and diagnostic information could be obtained on a small display tube.