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1.
J Acoust Soc Am ; 150(1): 241, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34340483

RESUMO

Double-strand breaks (DSBs) of giant DNA molecules after exposure to 1.0 MHz pulsed-wave ultrasound were quantitatively evaluated by single-molecule observation of giant DNA (T4 GT7 DNA; 166 kbp) through fluorescence microscopy. Aqueous solutions of DNA were exposed to ultrasonic waves with different sound pressures, repetition periods (1, 2, 5 ms), and pulse durations (5, 10, 50 µs). Below a threshold value of sound pressure, almost no double-strand breaks were generated, and above the threshold, the degree of damage increased in an accelerated manner as the pressure increased. DNA damage was much more severe for exposure to ultrasound with a shorter pulse duration. In addition, a longer pulse repetition period caused worse damage in DNA molecules. The effect of microbubbles on the damage induced by exposure to ultrasound had also been studied. While a result showed that a very small amount of microbubbles increased DSBs of DNA, this effect of microbubbles only weakly depended on their concentrations.


Assuntos
DNA , Ondas Ultrassônicas , Microbolhas , Ultrassonografia
2.
J Med Ultrason (2001) ; 48(2): 137-144, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33837866

RESUMO

PURPOSE: We previously reported that acoustic radiation force impulse (ARFI) with concomitant administration of perfluorobutane as an ultrasound contrast agent (UCA)-induced arrhythmias at a mechanical index (MI) of 1.8 or 4.0 in a rabbit model. The present study identified the location of arrhythmias with a MI < 1.8 using a new system that can transmit ARFI with B-mode imaging. METHODS: Under general anesthesia, six male Japanese white rabbits were placed in a supine position. Using this system, we targeted ARFI to the exact site of the heart. ARFI exposure with MI 0.9-1.2 was performed to the right or left ventricle of the heart 2 min after UCA injection. RESULTS: ARFI with a MI lower than previously reported to rabbit heart evoked extrasystolic waves with single UCA infusion. Arrhythmias were not observed using ARFI without UCA. Extrasystolic waves were observed significantly more frequently in the right ventricle group than in the left ventricle group, with arrhythmias showing reversed shapes. No fatal arrhythmias were observed. CONCLUSION: ARFI applied to simulate clinical conditions in rabbit heart evoked extrasystolic waves with single UCA infusion. The right ventricle group was significantly more sensitive to ARFI exposure, resulting in arrhythmias, than the left ventricle group. The shapes of PVCs that occurred in the right ventricle group and the left ventricle group were reversed. Ultrasound practitioners who use ARFI should be aware of this adverse reaction, even if the MI is below the previously determined value of 1.9.


Assuntos
Arritmias Cardíacas/induzido quimicamente , Arritmias Cardíacas/diagnóstico por imagem , Meios de Contraste/efeitos adversos , Técnicas de Imagem por Elasticidade/métodos , Fluorcarbonetos/efeitos adversos , Aumento da Imagem/métodos , Animais , Arritmias Cardíacas/fisiopatologia , Meios de Contraste/administração & dosagem , Modelos Animais de Doenças , Fluorcarbonetos/administração & dosagem , Coração/diagnóstico por imagem , Coração/fisiopatologia , Masculino , Coelhos
3.
J Med Ultrason (2001) ; 46(1): 35-43, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30443690

RESUMO

PURPOSE: Tissue characterization in terms of the differences in thermo-physical properties of biological tissues was investigated in this study. The objective was to measure the ratio of variation in sound velocity due to ultrasonic heating and to derive the relational expression between the ratio and thermo-physical properties. METHODS: The ratio of sound velocity variation before and after the temperature rise of tissue samples exposed to ultrasound was measured by ultrasonic pulse echo method. The thermo-physical properties were estimated for a tissue-mimicking material and porcine muscle and fat tissues due to theoretical expression. The transducer for heating had a resonance frequency of 3.2 MHz, and the transducer for measurement of sound velocity variation had a resonance frequency of 5.2 MHz. RESULTS: In the phantom study, the measured values of the temperature rise agreed with the values calculated by a finite element method (FEM). The estimated values of the temperature rise from the sound velocity variations of muscle and fat tissues were 0.36 °C and 1.1 °C, respectively. Also, the estimated values of thermo-physical properties agreed with the reference values within an error of 10%. CONCLUSIONS: The thermo-physical properties of the porcine tissues were measured by sound velocity variation due to ultrasonic heating within the safety regulations.


Assuntos
Temperatura Alta , Ultrassonografia/métodos , Tecido Adiposo/diagnóstico por imagem , Animais , Músculo Esquelético/diagnóstico por imagem , Imagens de Fantasmas , Som , Suínos , Temperatura , Transdutores
4.
J Med Ultrason (2001) ; 43(4): 481-5, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27401323

RESUMO

PURPOSE: Acoustic radiation force (ARF) elastography has recently become available. The previous animal studies have revealed lung injuries induced by diagnostic ultrasound, but the effects on the lung resulting from exposure to ultrasound with ARF are unknown. This study aimed to assess the risk of lung injury associated with ultrasound with ARF. METHODS: A focused 2.5-MHz transducer that emits ultrasound with ARF was used. A rabbit was anesthetized, and the transducer was placed in the right subcostal region. Exposure settings of mechanical index (MI) 0.80, pulse duration 10 ms, pulse repetition time 5 s, and exposure time 150 s were applied. RESULTS: One red spot (7 × 6 mm) was observed on the surface of the right lung corresponding to the area of exposure. Alveolar hemorrhage was observed microscopically. This lesion was visible across a range of 20-170 µm in depth from the pleural surface. CONCLUSION: The first example of lung hemorrhage induced by ultrasound with ARF was observed in this study. This observation suggests the possibility of lung injury in humans when ARF elastography is applied with the transducer directed toward the lung. Further studies are needed to determine the safety of this modality.


Assuntos
Técnicas de Imagem por Elasticidade/efeitos adversos , Lesão Pulmonar/etiologia , Ondas Ultrassônicas/efeitos adversos , Ultrassonografia/efeitos adversos , Animais , Técnicas de Imagem por Elasticidade/métodos , Hemorragia/diagnóstico por imagem , Hemorragia/etiologia , Hemorragia/patologia , Pulmão/diagnóstico por imagem , Pulmão/patologia , Lesão Pulmonar/diagnóstico por imagem , Lesão Pulmonar/patologia , Masculino , Coelhos , Ultrassonografia/métodos
5.
J Med Ultrason (2001) ; 43(4): 473-9, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27334036

RESUMO

PURPOSE: The experimental investigation of an optical fiber Bragg grating (FBG) sensor for biomedical application is described. The FBG sensor can be used to measure sound pressure and temperature rise simultaneously in biological tissues exposed to ultrasound. The theoretical maximum values that can be measured with the FBG sensor are 73.0 MPa and 30 °C. METHODS: In this study, measurement of sound pressure up to 5 MPa was performed at an ultrasound frequency of 2 MHz. A maximum temperature change of 6 °C was measured in a tissue-mimicking material. RESULTS: Values yielded by the FBG sensor agreed with those measured using a thermocouple and a hydrophone. CONCLUSION: Since this sensor is used to monitor the sound pressure and temperature simultaneously, it can also be used for industrial applications, such as ultrasonic cleaning of semiconductors under controlled temperatures.


Assuntos
Tecnologia de Fibra Óptica/métodos , Fibras Ópticas , Pressão , Som , Temperatura , Desenho de Equipamento , Ultrassom/instrumentação , Água
6.
J Med Ultrason (2001) ; 43(1): 3-7, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26703160

RESUMO

PURPOSE: Acoustic radiation force impulse (ARFI) is a modality for elasticity imaging of various organs using shear waves. In some situations, the heart is a candidate for elasticity evaluation with ARFI. Additionally, an ultrasound contrast agent (UCA) provides information on the blood flow conditions of the cardiac muscle. This study aimed to evaluate ARFI's effect on the heart concomitantly with UCA administration (i.e., perfluorobutane). METHODS: Ultrasound with ARFI was applied to the hearts of male Japanese white rabbits (n = 3) using a single-element focused transducer with or without UCA administration. They were exposed to ultrasound for 0.3 ms with a mechanical index (MI) of 1.8. UCA was administered in two ways: a single (bolus) injection or drip infusion. Electrocardiograms were recorded to identify arrhythmias during ultrasound exposure. RESULTS: Extrasystolic waves were observed following ultrasound exposure with drip infusion of UCA. Life-threatening arrhythmia was not observed. The frequency of the extra waves ranged from 4.2 to 59.6 %. With bolus infusion, extra waves were not observed. CONCLUSIONS: Arrhythmogenicity was observed during ultrasound (MI 1.8) with ARFI and concomitant administration of UCA in rabbits. Although the bolus administration of UCA was similar to its clinical use, which may not cause extra cardiac excitation, cardiac ultrasound examinations with ARFI should be carefully performed, particularly with concomitant use of UCA.


Assuntos
Arritmias Cardíacas/etiologia , Meios de Contraste/administração & dosagem , Ecocardiografia/efeitos adversos , Ecocardiografia/métodos , Técnicas de Imagem por Elasticidade/efeitos adversos , Técnicas de Imagem por Elasticidade/métodos , Animais , Arritmias Cardíacas/fisiopatologia , Ecocardiografia/instrumentação , Técnicas de Imagem por Elasticidade/instrumentação , Eletrocardiografia , Coração/fisiopatologia , Masculino , Coelhos , Fluxo Sanguíneo Regional
8.
J Med Ultrason (2001) ; 42(1): 39-46, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26578488

RESUMO

PURPOSE: Acoustic radiation force impulse (ARFI) has recently been used for tissue elasticity measurement and imaging. On the other hand, it is predicted that a rise in temperature occurs. In-situ measurement of temperature rise in animal experiments is important, yet measurement using thermocouples has some problems such as position mismatch of the temperature measuring junction of the thermocouple and the focal point of ultrasound. Therefore, an in-situ measurement system for solving the above problems was developed in this study. METHODS: The developed system is composed mainly of an ultrasound irradiation unit including a custom-made focused transducer with a through hole for inserting a thin-wire thermocouple, and a temperature measurement unit including the thermocouple. RESULTS: The feasibility of the developed system was evaluated by means of experiments using a tissue-mimicking material (TMM), a TMM containing a bone model or a chicken bone, and an extracted porcine liver. The similarity between the experimental results and the results of simulation using a finite element method (FEM) implied the reasonableness of in-situ temperature rise measured by the developed system. CONCLUSION: The developed system will become a useful tool for measuring in-situ temperature rise in animal experiments and obtaining findings with respect to the relationship between ultrasound irradiation conditions and in-situ temperature rise.


Assuntos
Técnicas de Imagem por Elasticidade , Temperatura Alta , Animais , Osso e Ossos/efeitos da radiação , Fígado/efeitos da radiação , Modelos Biológicos
9.
J Med Ultrason (2001) ; 42(1): 47-50, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26578489

RESUMO

PURPOSE: Acoustic radiation force (ARF) impulse can be used to estimate the elasticity of cardiac muscle. The purpose of this study was to evaluate the effect of ARF on the heart with concomitant administration of the ultrasound contrast agent (UCA) perfluorobutane for recently developed elasticity imaging such as shear wave imaging. METHODS: Ultrasound with ARF was applied to the heart of Japanese white rabbit with or without UCA administration. During the exposure, electrocardiographs were recorded. RESULTS: Following the exposure of ultrasound with a duration of 10 ms and a mechanical index (MI) of 4.0 to the heart, extra waves (QRS complex) were observed only after UCA administration. Although life-threatening arrhythmia was not observed, a greater increase in the frequency of the extra waves was observed following a drip infusion compared with a single (bolus) UCA infusion. In addition, 16.3 % of extra waves were followed by arterial pressure pulse. CONCLUSIONS: Cardiac ultrasound with higher MI and longer duration should be carefully considered, particularly with the concomitant use of UCA and higher MI.


Assuntos
Técnicas de Imagem por Elasticidade , Coração/efeitos da radiação , Animais , Arritmias Cardíacas/diagnóstico por imagem , Arritmias Cardíacas/etiologia , Meios de Contraste , Técnicas de Imagem por Elasticidade/efeitos adversos , Técnicas de Imagem por Elasticidade/métodos , Fluorcarbonetos , Masculino , Coelhos
11.
J Med Ultrason (2001) ; 36(2): 53-60, 2009 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27277084

RESUMO

PURPOSE: The aim of this study was realization of a broadband measurement system that is capable of effectively carrying out a frequency compound method. In the present method, the secondary wave components of difference and sum frequencies are generated along with the higher harmonic components through the nonlinear interaction of two-frequency ultrasound. A multiple-frequency beam is generated together with the initially radiated frequency components. METHODS: For the structure of a transducer capable of simultaneously radiating two sound waves with different frequencies, a coaxial arrangement of a circular-disc piezoelectric transducer and a ring piezoelectric transducer was designed. The radiating frequencies chosen were 2 and 8 MHz. In addition to the 4-MHz second harmonic sound of the 2-MHz primary sound, sounds of the 6-MHz difference frequency and the 10-MHz sum frequency can be generated. RESULTS: By measuring the acoustic pressure distribution, the formation of a multiple-frequency beam was confirmed. The signal-to-noise ratio in an agar-gel phantom image was increased by 5-6 dB with application of the frequency compound method. The validity of the proposed method was demonstrated through the generation of a human finger image. Further, it was found that the influence of the Doppler effect was small enough that almost all the secondary waves were attributable to the nonlinear propagation of sounds. CONCLUSIONS: A multiple-frequency sound beam was realized by radiating a two-frequency sound. The effectiveness of the presented method was demonstrated through actual imaging.

12.
J Med Ultrason (2001) ; 33(2): 71-6, 2006 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27277724

RESUMO

PURPOSE: We constructed an ultra-broadband ultrasonic transducer in a mechanical sector device, and prototyped a system to generate real-time images with higher harmonics. The potential of the system to reduce speckle was also studied. METHODS: To efficiently detect the higher harmonic components in echo signals, in addition to the transmitting transducer, another transducer only for broadband reception is necessary. We constructed a receiving transducer by bonding a polyvinylidene fluoride (PVDF) high-polymer piezofilm to the radiation surface of the transmitting lead zirconate titanate (PZT) transducer. By building this PZT-PVDF bi-layered ultrasonic probe into a mechanical sector scanner of an ultrasonic diagnosis system, an ultra-broadband ultrasonic imaging system capable of real-time imaging was prototyped. RESULTS: Using images of phantoms in water acquired using the prototype system, the acquisition of higher harmonic images with less noise up to the fourth order was demonstrated. In addition, we confirmed that the logarithmic summation of harmonic components from the fundamental to the fourth harmonic effectively reduces speckle noise in the images. CONCLUSIONS: By obtaining an echo signal from phantoms using a PZT-PVDF bi-layered ultrasonic mechanical sector probe, real-time imaging was carried out, and the effectiveness of its higher harmonic components from the fundamental to the fourth harmonic was confirmed with respect to speckle reduction.

13.
Ultrasound Med Biol ; 30(11): 1511-6, 2004 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-15588961

RESUMO

To assess the feasibility of a new system that uses the finite amplitude method and makes possible the assessment of the degree of nonlinear generation in vivo we adopted a method for agar-gel phantoms, using varying lipid concentrations and human livers in vivo. Instead of calculating the nonlinearity parameter B/A value, we evaluated the h value, which is determined by plotting the measured values of the ratio of the amplitude of the second harmonic component to that of the fundamental component. The agar-gel phantoms of various lipid concentrations and 20 cases of normal and 21 cases of fatty liver were studied in this investigation. There was an almost linear agreement between the h value and the lipid concentration of the phantom. The h value (mean +/- SD) was 0.25 +/- 0.03 in normal liver and 0.35 +/- 0.05 in fatty liver. A statistically significant difference was found between them (p < 0.0001). This new system was considered to be usable for evaluating h in vivo as an indicator of the lipid content of the liver.


Assuntos
Lipídeos/análise , Fígado/diagnóstico por imagem , Ultrassom , Fígado Gorduroso/diagnóstico por imagem , Estudos de Viabilidade , Humanos , Modelos Teóricos , Imagens de Fantasmas , Ultrassonografia
14.
J Med Ultrason (2001) ; 31(2): 67-73, 2004 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27278576

RESUMO

PURPOSE: We set out to enhance the imaging of stents used for coronary coarctation surgery without imaging the reticulation of the stent. Because the stent is a reticulated structure, there is a relation between ultrasound wavelength and the interstice reticulation that produces the echo. METHODS: First we performed computer simulation by ultrasound frequency of transmitted signals to analyze this relation. Then, instead of controlling the transmitted wave, we processed the returned signals through a band-pass filter because of the difficulty of controlling the transmitted waves of diagnostic ultrasound equipment. Following this, we conducted experiments on an agar gel phantom containing a stent to verify the effectiveness of this method. RESULTS: The simulation confirmed that the stent was apparent when the ultrasonic wavelength equaled the product of an integer and twice the interval of the reticulation of the stent. Application of a band-pass filter of 0.8 to 1.5 MHz to the waveform returned from the agar gel phantom containing the stent. CONCLUSIONS: The effectiveness of this method in depicting the stent was confirmed.

15.
J Med Ultrason (2001) ; 30(2): 103-10, 2003 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27278165

RESUMO

We applied quantitative parameters in three-dimensional ultrasonic images to distinguish benign from malignant breast tumors in 29 benign cases including 8 cysts and 21 fibroadenomas, and 32 malignant cases including 23 ductal carcinomas, 2 special types of carcinoma, 1 malignant lymphoma and 6 others. This procedure involved simultaneously acquiring video data from real-time ultrasonic images and recording the original position and orientation of the probe. Both sets of data were fed directly into a desktop computer. Fuzzy reasoning and relaxation techniques were use to automatedly extract the shape of the tumor and render it in three dimensions. We then evaluated three parameters: 2D-D/W, the so-called depth-width ratio measured in B-mode images: 3D-D/W; and the S/V index ([surface area](3)/36π [volume](2)) calculated from the three-dimensional volume extracted with this system. All three parameters were significantly higher in the malignant group (averages: 0.81, 0.64, and 11.3, respectively) than in the benign group (averages: 0.62, 0.47, and 3.78, respectively). All three parameters were thus found to be useful in differentiating the two groups.

16.
J Med Ultrason (2001) ; 30(1): 21-9, 2003 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-27285151

RESUMO

We attempt to determine the possibility of classifying normal and cirrhotic livers by their internal echo texture alone, without using such basic ultrasonographic information as shape and surface character of the liver. We also assessed intraobserver reproducibility and interobserver agreement obtained using this classification to ascertain the diagnostic usefulness of the method. In this evaluation, we used both regional magnified B-mode images and binary black-and-white images, both derived from conventional B-mode images obtained from 10 patients with normal livers and 10 with cirrhotic livers. These 20 echograms were randomly divided into two groups and evaluated independently on two occasions by 12 observers who used the unaided eye and took only internal echo texture into consideration. Accuracy in distinguishing between normal and cirrhotic livers ranged from 41.7 percent to 100 percent. The intraobserver correlation coefficient r1 between evaluations of the regional magnified B-mode images was 0.63, while that for the binary black-and-white images was 0.80. Agreement between the decisions of the 12 observers in the first and second evaluations of the binary black-and-white images showedk values between 0 and 1.0 for binary black-and-white images and between -0.32 and 0.29 for regional magnified B-mode images. Subjective evaluation of normal and cirrhotic livers based on internal echo texture alone was possible: intraobserver correlation was good; and unexpectedly, agreement with black-and-white images was greater than that with the regional magnified B-mode images.

17.
Igaku Butsuri ; 21(3): 123-127, 2001.
Artigo em Japonês | MEDLINE | ID: mdl-12766297

RESUMO

This paper was reviewed in recent progress of medical ultrasonic technology. Obviously in 21 century we face to the second generation of ultrasonic technology in medicine. First of all, B-mode imaging and Doppler color flow mapping have been improved by the digital beam forming technology. This technology leads to high research activity in the field of image processing such as automated tumor segmentation. Harmonic imaging is also newly developed technology. This technique uses harmonic component of echoes while the ultrasound waves are traveling through the nonlinear media such as biological tissues so that high quality images are obtained. Contrast echo method is expected to detect small echo signals from slow and small blood flow. Harmonic power Doppler imaging using micro bubbles is expected to detect early stage of cancer. Three dimensional real time imaging is next generation of ultrasonic image diagnosis system. Two dimensional array is a key technology to realize this imaging. Finally, ultrasonic therapy is described.

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