Ultrasound Instrument Research Articles

Reply to “Letter to the editor: ‘Assessment of flow-mediated dilation in humans: a methodological and physiological guideline'”

reply: We would like to thank Mc Loughlin and Mc Loughlin (4a) for their response and for bringing attention to the appropriate selection of transducer operating frequency for flow-mediated dilation investigations. We agree that employing a transducer with a higher central frequency (i.e., 12 MHz) will yield a greater detail resolution in the axial plane when interrogating vessels such as the brachial artery, and this would provide a greater sensitivity in detecting small changes in flow-evoked vasodilatation. However, in our review (8), we discussed not only the brachial artery but also the common femoral (9), profunda femoris (12), superficial femoral (1, 2, 10, 12), popliteal (5, 6, 11), and posterior tibial (3, 7) arteries. When these lower-limb vessels are insonated at an optimal region in terms of flow conditions, for example, at a distance where entrance effects are minimized, the artery depth is often greater than that expected for a typical brachial artery. Given that the average attenuation coefficient is 0.5 dB·cm−1·MHz−1 (4), there is considerable degradation of image quality when employing a high-frequency probe while imaging a deeper lying vessel. This can render the image unusable when combined with automated analysis software. The subsequent trade-off between detail resolution and depth penetration is a further consideration for researchers when performing flow-mediated dilation investigations; however, the minimum transducer recommended is 7.5 MHz for all peripheral arteries so as to maintain adequate detail resolution. Certainly, we advocate the use of higher transducer frequencies (i.e., 12 MHz) when investigating more superficial vessels such as the brachial and radial arteries.

Association of abdominal visceral adiposity and thigh sarcopenia with changes of arteriosclerosis in haemodialysis patients

In haemodialysis (HD) patients, abdominal visceral fat is accumulated while lean body mass is decreased irrespective of their body mass indexes (BMI). However, it is poorly understood which changes of fat and muscle masses are more associated with changes of arteriosclerosis. We aimed at examining the associations of abdominal visceral fat and thigh muscle masses with markers of arteriosclerosis in chronic HD patients in a cross-sectional fashion. We measured abdominal visceral fat mass area (AVFA), abdominal subcutaneous fat mass area (ASFA), thigh muscle area (TMA) and TMA standardized for femoral shaft area (TMA/FSA) by computed tomography (CT) in 161 HD patients (age: 61 ± 11 years, time on HD: 12 ± 10 years, male/female = 113/48, non-diabetes/diabetes = 127/34). We also investigated carotid artery intima-media thickness (CA-IMT) using the ultrasound instrument, and brachial-ankle pulse wave velocity (baPWV), cardio-ankle vascular index (CAVI) and ankle-brachial pressure index (ABI) using the waveform device (CAVI-VaSera VS-1000). AVFA was significantly and positively related to CA-IMT in both non-diabetic (r = 0.23, P < 0.05) and diabetic HD patients (r = 0.38, P < 0.05). There was a significant and positive correlation between AVFA and hs-CRP in all patients (r = 0.26, P < 0.01). ASFA was also significantly correlated with CA-IMT (r = 0.53, P < 0.01) in diabetic HD patients. TMA/SFA ratio was negatively associated with CA-IMT (r = - 0.21, P < 0.05), while positively with ABI (r = 0.28, P < 0.01) in non-diabetic patients. TMA/SFA ratio was inversely related to baPWV (r = - 0.41, P < 0.01) and CAVI (r = - 0.41, P < 0.05) in diabetic HD patients. Multiple regression analysis revealed that AVFA was a significant determinant of CA-IMT. TMA/AFA was also significantly associated with CA-IMT, baPWV, CAVI and ABI. Accumulated abdominal visceral fat is associated with CA-IMT. In addition, reduced thigh muscle mass area is independently related to CA-IMT, baPWV, CAVI and ABI, suggesting that sarcopenia in the leg is closely associated with systemic changes of arteriosclerosis in HD patients.

Ultrasound Physics and Instrumentation for Pathologists

Interest in pathologist-performed ultrasound-guided fine-needle aspiration is increasing. Educational courses discuss clinical ultrasound and biopsy techniques but not ultrasound physics and instrumentation. To review modern ultrasound physics and instrumentation to help pathologists understand the basis of modern ultrasound. A review of recent literature and textbooks was performed. Ultrasound physics and instrumentation are the foundations of clinical ultrasound. The key physical principle is the piezoelectric effect. When stimulated by an electric current, certain crystals vibrate and produce ultrasound. A hand-held transducer converts electricity into ultrasound, transmits it into tissue, and listens for reflected ultrasound to return. The returning echoes are converted into electrical signals and used to create a 2-dimensional gray-scale image. Scanning at a high frequency improves axial resolution but has low tissue penetration. Electronic focusing moves the long-axis focus to depth of the object of interest and improves lateral resolution. The short-axis focus in 1-dimensional transducers is fixed, which results in poor elevational resolution away from the focal zone. Using multiple foci improves lateral resolution but degrades temporal resolution. The sonographer can adjust the dynamic range to change contrast and bring out subtle masses. Contrast resolution is limited by processing speed, monitor resolution, and gray-scale perception of the human eye. Ultrasound is an evolving field. New technologies include miniaturization, spatial compound imaging, tissue harmonics, and multidimensional transducers. Clinical cytopathologists who understand ultrasound physics, instrumentation, and clinical ultrasound are ready for the challenges of cytopathologist-performed ultrasound-guided fine-needle aspiration and core-needle biopsy in the 21st century.

E0019 Study on the changes of matrix metalloproteinase-9 and high sensitive C-reactive protein in patients with carotid intima-media thickness

ObjectiveTo investigate the relationship between matrix metalloproteinase-9, high sensitive C-reactive protein and carotid intima-media thickness.Methods180 patients were selected. High-resolution ultrasound was used to scan carotid, brachial arteries of all patients...

The 18‐week fetal examination and detection of anomalies

From its beginning in the fifties the use of ultrasound in gynaecology and obstetrics has expanded extensively. Ultrasound technology has taken us from a time when the mother was our prime focus to the present where it is the unborn baby. Ultrasound assessments may have significant consequences for pregnancy care by optimizing the time, the mode and the location of the delivery as well as preparing the postnatal staff for a prenatally defined fetal problem. A major factor in the development was the groundbreaking work of an obstetrician, Ian Donald, and an engineer, Tom Brown, at Queen Mother's Hospital in Glasgow, who produced an ultrasound instrument called the Diasonograph. The first screening program offering a systematic ultrasound examination to a large pregnant population began in Malmoe, in 1973 and aimed to detect twins. Since then the examination has evolved over the years to include a systematic evaluation of the intrauterine contents. A number of randomized controlled trials have been reported and several large studies have reported the efficiency of routine fetal examinations for the detection of anomalies. Detection rates for the various subsets are presented. The learning curve regarding the ability to detect anomalies and the importance of proper training has also been shown. The procedure 'routine fetal examination' has been significant in supporting the continuous development of fetal medicine. The consequences of the improved dating of every pregnancy and the in utero transport of a sick fetus rather than an emergency transportation of a sick neonate, have an established evidence base. Ultrasound technology has had a remarkable ability to trigger great technical minds to move the technology forward year after year. Through a continuous cooperation between technicians and clinicians, this impressive technology of ultrasound will continue to support our work for the unborn child.

Piezosurgery® for removal of symptomatic ear osteoma

Piezosurgery is an ultrasound instrument (24.7-29.5 kHz) that is able to cut the bone without necrosis and nonmineralized tissue damage. The aim of this work has been to determine the applicability and efficiency of the piezoelectric device in the excision of symptomatic ear osteomas. 10 patients affected by osteoma of the external auditory canal (EAC) (6 right, 4 left) were enrolled. Patients underwent excision of the EAC osteoma through a transcanal approach, with the piezoelectric device. Before and 6 months after surgery, all the patients underwent pure-tone audiometry, tympanometry, transient-evoked otoacoustic emissions, distortion product otoacoustic emissions, auditory brainstem response, and electronystamographic recording. The piezoelectric device provided excellent control without side effects on the adjacent structures of the external, middle and inner ear. The piezoelectric device is a new bony scalpel using the microvibrations at ultrasonic frequency so that soft tissue (nerve, vessel, dura mater, skin, etc.) will not be damaged even on accidental contact with the cutting tip. A feature of the piezoelectric device is its good manageability, which makes it easy for a well-trained otologic surgeon to create a straight osteotomy line: this renders the piezoelectric device suitable for bone surgery and for removal osteomas of the EAC.

Estimation of the viscoelastic properties of vessel walls using a computational model and Doppler ultrasound

Human arteries affected by atherosclerosis are characterized by altered wall viscoelastic properties. The possibility of noninvasively assessing arterial viscoelasticity in vivo would significantly contribute to the early diagnosis and prevention of this disease. This paper presents a noniterative technique to estimate the viscoelastic parameters of a vascular wall Zener model. The approach requires the simultaneous measurement of flow variations and wall displacements, which can be provided by suitable ultrasound Doppler instruments. Viscoelastic parameters are estimated by fitting the theoretical constitutive equations to the experimental measurements using an ARMA parameter approach. The accuracy and sensitivity of the proposed method are tested using reference data generated by numerical simulations of arterial pulsation in which the physiological conditions and the viscoelastic parameters of the model can be suitably varied. The estimated values quantitatively agree with the reference values, showing that the only parameter affected by changing the physiological conditions is viscosity, whose relative error was about 27% even when a poor signal-to-noise ratio is simulated. Finally, the feasibility of the method is illustrated through three measurements made at different flow regimes on a cylindrical vessel phantom, yielding a parameter mean estimation error of 25%.

A method for free-field transfer calibration of electret microphones at ultrasound frequencies in air using a stable broad band ultrasound source.

A rotating turbulence screen wheel sound source, now in use in the air ultrasound instrument industry for product quality control, provides a steady source of broad band ultrasound. This source is broad band through at least 100 kHz. It is calibrated as a secondary standard, using a one-quarter inch condenser microphone, grid removed, normal incidence, and corrected for free-field conditions per the microphone manufacturer free-field response. Sound pressure amplitude is measured at a distance of 500 mm and from 1 to 100 kHz in 1-kHz FFT bins. Calibration site sound absorption by humid air is calculated to correct the emitted sound pressure values to be reinserted for the user test site air temperature and humidity. Transfer calibrations of two electret condenser microphones are shown. Microphone phase response measurement methods will also be investigated and discussed.

Confiabilidade da medida de espessuras musculares pela ultrassonografia

OBJETIVO: Determinar a confiabilidade das medidas de espessuras dos músculos flexores e extensores do cotovelo e joelho pela ultrassonografia (US), quantificando o erro típico associado a essas medidas (ETM). MÉTODOS: A confiabilidade (duas medidas interdias) foi determinada em 15 voluntários aparentemente saudáveis (oito mulheres, 33,9 ± 11,4 anos, 76 ± 21kg, 170 ± 10cm). As imagens da musculatura flexora (FC) e extensora do cotovelo (EC) e flexora (FJ) e extensora do joelho (EJ) foram obtidas pela US bidimensional no modo B, utilizando transdutor de 7,5MHz. As espessuras do tecido muscular compreendidas entre as interfaces com o osso e com o tecido adiposo foram medidas em sítios anatômicos identificados e registrados para ser repetidos na segunda medida. RESULTADOS: A ANOVA não identificou diferenças significativas entre as medidas repetidas. Os coeficientes de correlação intraclasse foram FC = 0,970, EC = 0,971, FJ = 0,555 e EJ = 0,929 (P &lt; 0,05 para todos). Os coeficientes de variação foram de 3,9%, 6,1%, 6,6 % e 4,6%, e os ETM 1,3mm, 1,6mm, 4,9mm e 1,9mm, respectivamente, para espessuras de FC, EC, FJ e EJ. A análise dos gráficos de Bland-Altman apontou que as variáveis não apresentaram erro heterocedástico. CONCLUSÃO: As medidas de espessuras musculares de FC, EC e EJ apresentaram alta confiabilidade, possibilitando seu uso para intervenções como programas de dieta, treinamento físico ou reabilitação. No entanto, o uso da medida de FJ não deve ser recomendada, pois mostrou baixa confiabilidade e alto ETM.

RBC motion and the basis of ultrasound Doppler instrumentation.

Ultrasonography has become one of the most popular techniques for noninvasive body assessment. The advent of sophisticated Doppler imaging has added an “information about blood flow” dimension. However, searching for complex details, despite enhanced system design and capabilities, place an increased demand on the operator. Examination technique and equipment settings are potential sources of error and therefore to obtain and interpret Doppler indices well it is essential to understand the physics of the Doppler principle and the dynamics of blood flow.

건강 관련 요인이 자궁근종에 미치는 영향

여성의 자궁근종에 대한 유병률을 초음파진단장비로 확인하고 건강 관련 요인과 자궁근종과의 상관관계를 분석하여 건강 관련 요인이 자궁근종의 발생에 미치는 구체적인 발생 요인을 확인하고자 한다. 자궁근종이 진단된 모집단과 자궁근종이 없는 대조군을 대상으로 자가 기입식 설문조사를 실시한 결과 초음파진단 장비로 진단된 자궁근종의 유병률은 29.7%로 나타났으며, 자궁근종군의 연령분포는 40~49세가 41.4%로 가장 높게 나타났다(p<0.05). 자궁근종의 유병률에 영향을 미치는 각 요인에 대하여 조사한 결과, 연령, 결혼력, 직업의 활동량, 생활의 만족도, 체중, 비만도, 분만력, 수유, 유산, 피임 등은 자궁근종과의 상관관계에서 통계적으로 유의하였다.(p<0.05) Prevalence of female uterine myoma was determined using ultrasound diagnosis instrument, and correlation between health-related factors and uterine myoma was analyzed to investigate concrete factors for production of uterine myoma. Subjects in uterine myoma group and control group were asked to answer the questionnaire survey. The results were determined that prevalence of uterine mayma was 29.7%, and 40~49 aged group showed the highest level of uterine myoma by 41.4%. (p<0.05). The analysis showed that there were significant correlations between uterine myoma and collected variables such as age, marital status, occupational activity level, satisfaction level of life, weight, obesity, delivery history, breast feeding, abortion, and contraceptive experience (p<0.05).

A Randomized Clinical Evaluation of Ultrasound Bone Surgery Versus Traditional Rotary Instruments in Lower Third Molar Extraction

The purpose of this study was to investigate and compare, in a randomized and controlled clinical trial, the use of ultrasound bone surgery devices and the use of rotary instruments in lower third molar extractions. We selected 26 patients (12 women and 14 men) for this study; the mean age was 31.2 years (range, 24-45 years). A randomized clinical trial was planned. Patients in the control group received treatment with the conventional rotary instruments; patients in the test group received treatment with the ultrasound bone surgery tools. Twenty-six third molars were allocated to the test and control groups according to a computer-generated randomization list. All the surgical procedures were performed by the same surgeon. Pain, trismus, cheek swelling, and number of analgesics taken were evaluated at baseline (before surgery) and at the first-, third-, fifth-, and seventh-day visits. Pain levels (evaluated on a visual analog scale) were higher in the control group when compared with the ultrasonic group; however, no statistically significant differences were found. On the contrary, the number of analgesics taken in the test group was significantly lower when compared with the control group. The occurrence of trismus was significantly higher in the control group when compared with the test group. The clinical values of cheek swelling were higher in the rotary group when compared with the ultrasound group at the fifth-day visit. This study showed that the use of ultrasound bone surgery for third molar extraction significantly reduced the occurrence of postsurgical trismus, the occurrence of swelling, and the number of analgesics taken after surgery.

Effect of Black-Currant Extract on Negative Lens-Induced Ocular Growth in Chicks

Aim: To evaluate the effects of orally administered black-currant (BC) extract on the enlargement of globe component dimensions induced in chicks by wearing negative lenses. Methods: Negative lenses (–8 D) were worn on the right eyes by 8-day-old chicks, and their fellow eyes acted as controls. BC extract and distilled water (vehicle control) were orally administered once a day for 3 days. To confirm the effect of BC anthocyanins (BCAs), they were intravenously administered once a day for 3 days. Dimensions of globe components of right eyes and fellow eyes were measured with an A-scan ultrasound instrument on the third day (day 4) after placement of the negative lenses. Results: Orally administered BC extract significantly inhibited enlargement of vitreous-chamber depth, axial and ocular lengths in a dose-dependent manner when compared to controls. Intravenously administered BCAs also inhibited elongation of vitreous-chamber depth and axial length when compared to controls. Conclusions: This is the first evidence that BC extract and BCAs could inhibit enlargement of globe component dimensions in a negative lens-induced chick myopia model.

Learning curve for Piezosurgery in well-trained otological surgeons

Objective Piezosurgery is an ultrasound instrument (24.7-29.5 kHz) capable of cutting bone without necrosis and nonmineralized tissue damage. The aim of this work has been to determine the time required for a well-trained surgeon to perform otological surgery with the piezoelectric device. Study Design Case series with planned data collection. Sixty-three patients affected by otosclerosis and 63 by chronic otitis media were enrolled. For each disease, patients were divided into three numerically equal groups, with each group assigned to a well-trained otological surgeon. Patients underwent stapedotomy (n = 63) and intact canal wall tympanoplasty (n = 63) with the piezoelectric device. Setting ENT Department, University of Genoa (Italy). Subjects and Methods We recorded “skin-to-skin” operation time, surgical success, surgical complication, and hospital stay duration. Before and one year after surgery, all patients underwent pure-tone audiometry, tympanometry, recording of transient-evoked otoacoustic emission, recording of distortion product otoacoustic emission, auditory brainstem response, and electronystamographic recording. Results In each surgical technique, the piezoelectric device provided excellent control without side effects on the adjacent structures of the middle and inner ear. Conclusion The piezoelectric device is a new bony scalpel that uses microvibrations at ultrasonic frequency so that soft tissue (nerve, vessel, dura mater, etc) will not be damaged even on accidental contact with the cutting tip. A feature of the piezoelectric device is its good manageability, which makes it easy for a well-trained otological surgeon to create a straight osteotomy line without any learning period: this renders the piezoelectric device suitable for bone surgery.

Assessment of sonographic quality of anal sphincter muscles in patients with faecal incontinence

The main application of endoanal ultrasonography (US) in evaluation of faecal incontinence is to identify surgically correctable sphincter defects. The aim of our study was to determine whether qualitative changes in echogenicity and in uniformity of internal (IAS) and external (EAS) anal sphincter muscles detected on endoanal US correlate with other anal laboratory tests and modified Wexner faecal incontinence functional score. Records on 99 patients having complete information on anorectal manometry, faecal incontinence scoring and available endoanal US imaging of the anal sphincters were included in statistical analysis. Anatomic appearance and changes in echogenicity of the anal sphincter muscles were recorded according to the proposed scoring system. Endoanal US defect and quality component scores for IAS and EAS as well as the total score were correlated with anal laboratory tests and incontinence score using Spearman's correlations test. There was a trend for correlation between IAS quality score and incontinence score (P = 0.06), but no correlation for IAS defect score. EAS defect score had a significant negative correlation with maximum squeeze pressure (MSP) (P = 0.031). Distal EAS quality score had a significant correlation with incontinence score (P = 0.002). EAS total score correlated with MSP (P = 0.02) and incontinence score (P = 0.006). Endoanal US total score was significantly correlated with incontinence score (P = 0.006), maximal resting (MRP) (P = 0.035) and MSP (P = 0.045) and high pressure anal canal zone length (P = 0.03). Sonographic morphology of anal sphincter muscles correlates with anal laboratory tests and functional incontinence score. Qualitative ultrasound scoring instrument may improve evaluation of patients with faecal incontinence.

Ultrasound imaging of the early fetus: is it safe?

Diagnostic ultrasound has an excellent safety record in general and, in particular, in obstetrics. As a form of energy, ultrasound has effects in insonated tissues that are caused by two main mechanisms: thermal and nonthermal (also known as mechanical). Onscreen indicators of these potential bioeffects are the thermal and mechanical indices. Biological effects of ultrasound have been reported in animals but no harmful effects have been demonstrated in human epidemiological studies. However, all epidemiological studies published so far are based on information obtained with pre-1992 machines, when acoustic intensities for fetal use of ultrasound instruments were allowed to be increased by a factor of almost eight. Many applications are used to scan the fetus and, increasingly, this is performed early in gestation, a time when the fetus is known to be particularly sensitive to external influences. While dating and location of the gestation and verification of the number of fetuses have long been employed i...

A Novel Ultrasound Microbubble Carrying Gene and Tat Peptide: Preparation and Characterization

Ultrasound-targeted microbubble destruction is a promising technology for the targeted gene delivery. The purpose of the present study is to prepare a novel lipid ultrasound microbubble-carrying gene and transactivating transcriptional activator (Tat) peptide and to investigate its transfection effect in vivo. Lipid ultrasound microbubbles were prepared using mechanical vibration, and the appearance, distribution, concentration, diameter, and zeta potential of the lipid ultrasound microbubbles were measured. The efficiencies of the microbubble carrying gene and Tat peptide were investigated using the fluorospectrophotometer. Contrast-enhanced ultrasonography was performed on normal rabbits to observe the duration and intensity of enhancement in myocardium. Quantitative analysis was detected using the DFY Ultrasound Image Analyzer. Transfection in vivo was performed using the CGZZ ultrasound gene transfection instrument. The expression of enhanced green fluorescent protein in the organs was observed using confocal laser scanning microscope. The diameter of the lipid microbubbles carrying gene and Tat was (2.3 +/- 0.4) mum, the concentration was (3.1 +/- 0.4) x10(9)/mL, and Zeta potential was (2.0 +/- 0.1) mV. The gene encapsulation efficiency of the lipid ultrasound microbubbles was 32%, and the Tat encapsulation efficiency was 35%. In vivo experiment showed that lipid ultrasound microbubbles could enhance the echo intensity and transfection efficiency. Lipid microbubbles containing gene and Tat peptide can be used as a new vehicle for gene transfection.

1133: Contrast-Enhanced Real-Time Harmonic Gray Scale Ultrasound Findings of Peripheral Intrahepatic Cholangiocarcinoma

To characterize the contrast-enhanced real-time harmonic gray scale ultrasound (CEUS) findings of peripheral intrahepatic cholangiocarcinoma (ICC) and to access the usefulness of CEUS in the diagnosis of ICC. Retrospective analysis of 33 patients with ICC who had undergone both preoperative CEUS. Sonographic examinations were performed with Technos DU8 and Philips IU22 ultrasound instruments and ultrasound contrast agent SonoVue. All ICC lesions enhanced in the arterial phase with an initial time of 14.59s±3.77s(5s-20s) and a peak enhancement time of 21.39s±5.00s(10s-30s). The time of lesions displaying isoechoic and hypoechoic comparing with the hepatic parenchyma were 29.84s±7.69s(14s-52s) and 40.13s±15.55s(20s-90s), respectively. Then all lesions presented hypoechoic in the portal and the late phase. Of the 33 patients,16 (48.5%) cases showed whole-lesion enhancement and 17 (51.5%) cases showed rim-like or thick bandlike enhancement. There were 63.6%(21/33) cases showing progressive dendritic and concentric filling of the contrast agent and 81.8%(27/33)cases showing heterogeneous enhancement during the peak enhancement. Of all patients, 51.5% (17/33) cases presented lobular appearance during the CEUS examination especially in the portal phase and parenchyma phase. The diagnostic accuracy of CEUS was 87.9% (29/33) if the diagnostic feature included early wash-in and wash-out, progressive dendritic enhancement and/or heterogeneous enhancement. There are some specific findings on CEUS which is useful in the diagnosis and differential diagnosis of this disease.

Interpolation of Medical Ultrasound Images From Coherent and Noncoherent Signals

Medical ultrasound imaging instrumentation typically performs image interpolation using the signals acquired after envelope extraction, i.e., noncoherent signals. This operation is completely satisfying when the Nyquist condition for spatial sampling is fulfilled. However, the maximum spatial frequency of a signal increases as a consequence of the envelope extraction, making it more difficult to fulfill the Nyquist condition. For this reason, this paper suggests the interpolation of signals before envelope extraction, i.e., the use of coherent data, and discusses the applicability of this procedure to actual ultrasound scanners. Emphasis is given to the linear-array imaging technique, and the adoption of windowed sinc functions as interpolation kernels with limited support is assessed. Moreover, the authors investigated the situation in which coherent signals are also undersampled, and perfect reconstruction is not at all possible. The investigation was carried out using a numerical study and a simulated imaging test, and it was supported by subjective and objective evaluations. It is concluded that, at a moderate undersampling level, the interpolation of coherent signals allows significantly better performance than the interpolation of noncoherent signals.

MO‐A‐213A‐01: Harmonic Imaging

The purpose of this course is to acquaint participants with recent signal processing techniques and modes on ultrasound instruments. Emphasis is on second harmonic imaging, a processing and display mode implemented on most scanners. Harmonic imaging was originally applied to enhance echo signals due to nonlinear scattering by ultrasound contrast agents. However, the modality is much more commonly used in “native tissue harmonic” mode, where echoes originating from nonlinear components of propagating acoustic beams are detected and displayed. The source of these echo signals and the advantages and disadvantages of harmonic imaging will be described. When applied effectively, harmonic imaging provides significant improvements in image quality compared to that obtained using conventional signal processing. A primary reason for harmonic imaging's improved image quality is reduction of acoustic noise caused by reverberations within overlying tissues. Other contributors to high quality ultrasound images include spatial and frequency compounding and speckle reduction. These techniques also will be described and placed in context with harmonic imaging.Learning ObjectivesAfter completing this course, participants will:1. Describe the origin of harmonic echo signals for both conventional and contrast agent imaging modes;2. Contrast resolution and penetration capabilities for harmonic imaging and linear imaging;3. Identify clinical situations where harmonic imaging is used advantageously;4. Describe how harmonic imaging is used to enhance detection of contrast agents;5. State the benefits of spatial and frequency compounding, and speckle reduction.