Tissue Harmonic Research Articles

A complex approach to continuous cardiac monitoring of neoadjuvant chemotherapy: Observational study

A complex approach to continuous cardiac monitoring of neoadjuvant chemotherapy: Observational study

Second-Generation Differential Tissue Harmonic Imaging Improves the Visualization of Renal Lesions.

To compare to three nonlinear imaging techniques to conventional, grayscale ultrasound imaging of renal lesions. Twenty adults with a known renal lesion and a body mass index >25 kg/m2 were enrolled in this prospective, institutional review board approved study. Each subject was imaged with an Aplio 500 scanner (Canon Medical Systems, Tokyo, Japan) using grayscale ultrasound, tissue harmonic imaging (THI) and two dual-frequency, differential tissue harmonic imaging modes (DTHI and DTHI-II, respectively). In total 184 images were scored by three independent and blinded observers for detail resolution, image quality, margin delineation, and depth penetration. Quantitative contrast-to-noise ratios (CNRs) were also calculated. Readers and CNR values showed that nonlinear imaging was superior to grayscale ultrasound (P < .0014). DTHI-II outperformed DTHI, THI, and grayscale ultrasound with respect to detail resolution, image quality, and margin delineation (P < .012). The depth penetration of DTHI and DTHI-II was similar (P=.16), but superior to grayscale ultrasound and THI (P < .001). Two observers saw improvements in detail resolution with DTHI-II over DTHI (P < .05), while image quality and margin delineation were considered similar by two readers (P > .07) and improved with DTHI-II by one (P < .017). DTHI-II improves the imaging of renal lesions compared to DTHI, THI, and grayscale ultrasound, albeit based on a limited sample size.

An Efficient Adaptive Method Based on Empirical Wavelet Transform for Ultrasound Tissue Harmonic Imaging

An Efficient Adaptive Method Based on Empirical Wavelet Transform for Ultrasound Tissue Harmonic Imaging

Phase in bubble echoes due to nonlinear response improves contrast in ultrasound images

The image quality of contrast-enhanced ultrasound (CEUS) is limited by the tissue harmonics generated from the nonlinear propagation of sound waves, even at low amplitudes. Amplitude modulation (AM) is typically implemented by firing a full aperture and two complimentary half apertures. A phase difference (ΔΦΑΜ) between the echoes from the full and half pulse has been observed which is lower for tissue than bubble echoes. This phase difference may be used as a segmentation criterion for tissues and bubbles to improve contrast to tissue ratio (CTR) of CEUS images. This technique may be further expanded by considering also the phase difference (ΔΦhalf) between the complementary half amplitude pulses of the AM scheme (ΔΦhalf). This additional phase difference results from the spatial differences of the complementary half amplitude fields. We considered the change in ΔΦhalf when using various aperture patterns for AM. We observed that ΔΦhalf increases as the complementary fields become spatially dissimilar. For certain aperture patterns, we found that the phase difference between the echoes of the complementary apertures was greater than that between the full and half pulse (ΔΦhalf i> ΔΦΑΜ) and that it further contributed to the image CTR.

The Role of Tissue Harmonic Ultrasonography and Computerized Tomography in the Diagnosis of Intraabdominal Cystic Lesions

Aim: Abdominal Ultrasonography (US) and Computed Tomography (CT) examinations are imaging methods frequently used in Radiology Clinics. During these examinations, cystic lesions are frequently detected in the abdomen. It is an important problem to identify and characterize the clinical significance of these cysts.Methods: The findings of 145 patients who underwent abdominal imaging in the US and CT units of the Istanbul Training and Research Hospital Radiology Clinic and were found to have cystic lesions were analyzed retrospectively. The CT findings of cystic lesions detected in the abdominal organs or the abdominal cavity were reviewed, and the contribution of the new US image acquisition method, Tissue Harmonic Imaging (THI), to the characterization of cysts was examined.Results: A total of 145 patients, 56 men (39.3%) and 89 women (60.7%) with cystic lesions in the abdomen, were included. We detected cystic lesions most frequently in the kidneys (n:68, 46.89%) and second most frequently in the liver (n:65; 44.82%). In addition, we detected cystic lesions in the spleen in 5 cases (3.44%), in the pancreas in 7 cases (4.82%), and in the abdominal cavity in 5 cases (3.44%). In all our cases, cystic lesions could be visualized in both THI imaging and CT examination.Conclusion: THI examination provides valuable information in characterizing cystic lesions, especially by showing the wall feature of the cyst, the internal septa and the presence of intra-cystic solid component, while CT examination especially shows the wall calcification and the presence of air in the abscess, as well as the intramural solid component.

What are the minimum requirements to establish proficiency in lung ultrasound training for quantifying B-lines?

AimsThe goal of this study was to determine the number of scans needed for novice learners to attain proficiency in B‐line quantification compared with expert interpretation.Methods and resultsThis was a prospective, multicentre observational study of novice learners, physicians and non‐physicians from three academic institutions. Learners received a 2 h lung ultrasound (LUS) training session on B‐line assessment, including lecture, video review to practice counting and hands‐on patient scanning. Learners quantified B‐lines using an eight‐zone scanning protocol in patients with suspected acute heart failure. Ultrasound (US) machine settings were standardized to a depth of 18 cm and clip length of 6 s, and tissue harmonics and multibeam former were deactivated. For quantification, the intercostal space with the greatest number of B‐lines within each zone was used for scoring. Each zone was given a score of 0–20 based on the maximum number of B‐lines counted during one respiratory cycle. The B‐line score was determined by multiplying the percentage of the intercostal space filled with B‐lines by 20. We compared learner B‐line counts with a blinded expert reviewer (five US fellowship‐trained faculty with > 5 years of clinical experience) for each lung zone scanned; proficiency was defined as an intraclass correlation of > 0.7. Learning curves for each learner were constructed using cumulative sum method for statistical analysis. The Wilcoxon rank‐sum test was used to compare the number of scans required to reach proficiency between different learner types.Twenty‐nine learners (21 research associates, 5 residents and 3 non‐US‐trained emergency medicine faculty) scanned 2629 lung zones with acute pulmonary oedema. After a mean of 10.8 (standard deviation 14.0) LUS zones scanned, learners reached the predefined proficiency standard. The number of scanned zones required to reach proficiency was not significantly different between physicians and non‐physicians (P = 0.26), learners with no prior US experience vs. > 25 prior patient scans (P = 0.64) and no prior vs. some prior LUS experience (P = 0.59). The overall intraclass correlation for agreement between learners and experts was 0.74 and 0.80 between experts.ConclusionsOur results show that after a short, structured training, novice learners are able to achieve proficiency for quantifying B‐lines on LUS after scanning 11 zones. These findings support the use of LUS for B‐line quantification by non‐physicians in clinical and research applications.

Interleaved Array Transducer with Polarization Inversion Technique to Implement Ultrasound Tissue Harmonic Imaging.

In ultrasound tissue harmonic imaging (THI), it is preferred that the bandwidth of the array transducer covers at least the fundamental frequency f0 for transmission and the second harmonic frequency 2f0 for reception. However, it is challenging to develop an array transducer with a broad bandwidth due to the single resonance characteristics of piezoelectric materials. In this study, we present an improved interleaved array transducer suitable for THI and a dedicated transducer fabrication scheme. The proposed array transducer has a novel structure in which conventional elements exhibiting f0 resonant frequency and polarization-inverted elements exhibiting 2f0 resonant frequency are alternately located, and the thicknesses of all piezoelectric elements are identical. The performance of the proposed method was demonstrated by finite element analysis (FEA) simulations and experiments using a fabricated prototype array transducer. Using the proposed technique, f0 and 2f0 frequency ultrasounds can be efficiently transmitted and received, respectively, resulting in a 90% broad bandwidth feature of the transducer. Thus, the proposed technique can be one of the potential ways to implement high resolution THI.

Diagnosis of Biliary Tract Disease Based on Ultrasound Tissue Harmonic Imaging

With the deepening of ultrasound imaging research, studying nonlinear phenomena in medical ultrasound will help people to further improve the existing diagnostic level. Harmonic imaging technology generated in recent years is an effective new technology for nonlinear acoustics in ultrasonic diagnosis. Patients with biliary tract lesions generally have few symptoms, which are often detected by chance during physical examination. Ultrasonography is currently the preferred diagnostic method for biliary tract disease. The application of tissue harmonic imaging (THI) can effectively eliminate many near-field misdiagnosed images, enhance the tissue echo of deep tissues or organs, and significantly improve signal-to-noise ratio and resolution. At the same time, it can better display the subtle features of biliary diseases, thereby reducing the rate of missed diagnosis and improving the accuracy of diagnosis. Therefore, this study aimed to observe the changes of ultrasound images in the lesions and surrounding tissues of several biliary lesions by ultrasound tissue harmonic imaging technology, and realized the diagnosis in the early stage of the disease by means of tissue harmonic imaging technology, then provided objective quantitative indicators for the diagnosis of biliary diseases. Also, this study confirmed that tissue harmonic imaging technology can significantly improve the ultrasound image resolution of biliary tract disease, clearly showing the sub-acute gallbladder wall, gallbladder wall, gallbladder cavity in the acute and chronic inflammation and the presence of subtle changes in the tumor. This can provide a rich diagnostic value for the clinic and has practical significance for clinical treatment.

Adaptive Ultrasound Tissue Harmonic Imaging Based on an Improved Ensemble Empirical Mode Decomposition Algorithm

Complete and accurate separation of harmonic components from the ultrasonic radio frequency (RF) echo signals is essential to improve the quality of harmonic imaging. There are limitations in the existing two commonly used separation methods, that is, the subjectivity for the high-pass filtering (S_HPF) method and motion artifacts for the pulse inversion (S_PI) method. A novel separation method called S_CEEMDAN, based on the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) algorithm, is proposed to adaptively separate the second harmonic components for ultrasound tissue harmonic imaging. First, the ensemble size of the CEEMDAN algorithm is calculated adaptively according to the standard deviation of the added white noise. A set of intrinsic mode functions (IMFs) is then obtained by the CEEMDAN algorithm from the ultrasonic RF echo signals. According to the IMF spectra, the IMFs that contain both fundamental and harmonic components are further decomposed. The separation process is performed until all the obtained IMFs have been divided into either fundamental or harmonic categories. Finally, the fundamental and harmonic RF echo signals are obtained from the accumulations of signals from these two categories, respectively. In simulation experiments based on CREANUIS, the S_CEEMDAN-based results are similar to the S_HPF-based results, but better than the S_PI-based results. For the dynamic carotid artery measurements, the contrasts, contrast-to-noise ratios (CNRs), and tissue-to-clutter ratios (TCRs) of the harmonic images based on the S_CEEMDAN are averagely increased by 31.43% and 50.82%, 18.96% and 10.83%, as well as 34.23% and 44.18%, respectively, compared with those based on the S_HPF and S_PI methods. In conclusion, the S_CEEMDAN method provides improved harmonic images owing to its good adaptivity and lower motion artifacts, and is thus a potential alternative to the current methods for ultrasonic harmonic imaging.

Application of 14-MHz Ultrasonography with Tissue Harmonic Imaging to Determine Posterior Capsule Integrity in Traumatic Cataract.

Purpose To report the application of 14-MHz ultrasonography with tissue harmonic imaging (14 MHz + THI) to determine the integrity of the posterior capsule (PC) in traumatic cataract (TC). Methods Patients with TC who were scheduled to undergo cataract extraction and whose PC could not be observed by slit lamp examination were included in the study. The status of the PC was determined by 14 MHz + THI before cataract extraction and confirmed during surgery. The results regarding PC integrity obtained from 14 MHz + THI and intraoperative direct observation were compared. Result The study enrolled 52 eyes of 52 patients (49 men and 3 women), with a mean age of 42.15 years ± 11.23 (SD). The nature of the trauma was blunt (3 eyes) or sharp (49 eyes). The 14 MHz + THI method showed 21 PCs to be intact and 31 to have ruptured before cataract surgery. During surgery, 23 PCs were observed to be intact, while 29 PCs were ruptured. 27 PCs were ruptured and 19 were intact, as determined by the two methods. The 14 MHz + THI observations were consistent with the intraoperative observations of the PC (kappa = 0.764), with no significant difference between the two methods (P=0.687). The sensitivity, specificity, and accuracy of 14 MHz + THI for observation of the PC were 93.10%, 82.60%, and 88.46%, respectively. Conclusion The 14 MHz + THI method can accurately reveal the integrity of the PC in TC. It has important clinical value in the selection of cataract surgery methods and the prediction of complications during TC surgery.

AIUM Practice Parameter for the Performance of Point-of-Care Ultrasound Examinations.

AIUM Practice Parameter for the Performance of Point-of-Care Ultrasound Examinations.

Dual-Element Intravascular Ultrasound Transducer for Tissue Harmonic Imaging and Frequency Compounding: Development and Imaging Performance Assessment.

For accurate diagnosis of atherosclerosis, the high spatial and contrast resolutions of intravascular ultrasound (IVUS) images are a key requirement. Increasing the center frequency of IVUS is a simple solution to meet this requirement. However, this leads to a reduction in imaging depth due to the frequency-dependent attenuation of ultrasound. Here, we report a recently developed dual-element IVUS transducer for tissue harmonic imaging (THI) and frequency compounding to increase the spatial and contrast resolutions of IVUS images, while maintaining the imaging depth to assess the overall morphological change of blood vessels. One 35-MHz element is used for producing general IVUS images and the other 70-MHz element is for receiving the second harmonic signals induced by the 35-MHz ultrasound. The fundamental and second harmonic signals can also be used for frequency compound imaging to further improve contrast resolution. The spatial and contrast resolutions achieved by the developed transducer were evaluated through wire and tissue-mimicking phantom imaging tests. Additionally, the images of a stent deployed in a tissue-mimicking phantom and an excised pig artery were acquired to assess clinical usefulness of the transducer. The results demonstrated that the developed IVUS transducer enables us to simultaneously examine the overall morphological change of blood vessels by the 35-MHz ultrasound images and the near vessel layers such as the intima, the media, and the adventitia by either THI or compound images with high spatial and contrast resolutions. In addition, the developed transducer facilitates the simultaneous acquisition of 35- and 70-MHz fundamental images when needed. The developed dual-element IVUS transducer makes it possible to fully realize the potential benefits of IVUS in the diagnosis of atherosclerosis.

Abdominal Sonography: Evaluation of Image Quality in Patients with Varying BMI Using Tissue Harmonic Imaging and Standard Sonography

Abdominal Sonography: Evaluation of Image Quality in Patients with Varying BMI Using Tissue Harmonic Imaging and Standard Sonography

Development of Dual-Frequency Oblong-Shaped-Focused Transducers for Intravascular Ultrasound Tissue Harmonic Imaging.

Tissue harmonic imaging (THI), an essential mode of commercial ultrasound imaging scanners, can provide images with high spatial and contrast resolutions. For THI, the frequency spectrum of a transducer is generally divided for the transmission of fundamental signal and the reception of its second harmonic. Therefore, it is difficult to use the THI mode for intravascular ultrasound (IVUS) imaging because typical IVUS transducers have a narrow -6-dB fractional bandwidth of about 50%. Due to its small aperture (about 0.5 mm) and the strength of IVUS being too weak, it is difficult to construct a high-quality tissue harmonic image. In this paper, we report a recently developed dual-frequency oblong-shaped-focused IVUS transducer for high-quality intravascular THI; the transducer consists of three elements arranged side by side in the horizontal (i.e., elevation) direction. The two outer elements with a center frequency of 35 MHz are responsible for ultrasound transmission and the center element has a center frequency of 70 MHz for the reception of the second-harmonic signals. All three elements have a spherical shape with a radius of 3 mm to efficiently generate harmonics in the region of interest. This configuration of the developed IVUS transducer was determined to facilitate high-quality THI, which was based on the results of Field II simulation and finite-element analysis. The images of wires and a tissue-mimicking phantom indicated that the tissue harmonic images produced by the developed transducer have not only a high spatial resolution but also a deep imaging depth, compared to the 35- and 70-MHz fundamental images.

The Role of Microbubble Echo Phase Lag in Multipulse Contrast-Enhanced Ultrasound Imaging.

In this paper, we assess the importance of microbubble shell composition for contrast-enhanced imaging sequences commonly used on clinical scanners. While the gas core dynamics are primarily responsible for the nonlinear harmonic response of microbubbles at diagnostic pressures, it is now understood that the shell rheology plays a dominant role in the nonlinear response of microbubbles subjected to low acoustic pressures. Of particular interest here, acoustic pressures of tens of kilopascal can cause a reversible phase transition of the phospholipid coatings from a stiff elastic organized state to a less stiff disorganized buckled state. Such a transition from elastic to buckled shell induces a steep variation of the shell elasticity, which alters the microbubble acoustic scattering properties. We demonstrate in this paper that this mechanism plays a dominant role in contrast pulse sequences that modulate the amplitude of the insonifying pulse pressure. The contrast-to-tissue ratio (CTR) for amplitude modulation (AM), pulse inversion (PI), and amplitude modulation pulse inversion (AMPI) is measured in vitro for Definity, Sonazoid, both lipid-encapsulted microbubbles, and the albumin-coated Optison. It is found that pulse sequences using AM significantly enhanced the nonlinear response of all studied microbubbles compared to PI (up to 15 dB more) when low insonation pressures under 200 kPa were used. Further investigation reveals that the origin of the hyperechoicity is a small phase lag occurring between the echoes from the full-and half-amplitude driving pulses, and that the effect could be attributed to the shell softening dynamics of lipid and albumin coatings. We assess that this additional phase in microbubble ultrasound scattering can have a dominant role in the CTR achieved in contrast sequences using AM. We also show that the pressure dependent phase lag is a specific marker for microbubbles with no equivalent in tissue, which can be used to segment microbubbles from the tissue harmonics and significantly increase the CTR.

Tissue Harmonic Imaging Compared with Conventional BMode Ultrasound, Biphasic CECT and Tissue Diagnosis in Evaluation of Pancreatic Masses

Tissue Harmonic Imaging Compared with Conventional BMode Ultrasound, Biphasic CECT and Tissue Diagnosis in Evaluation of Pancreatic Masses

Comparison of total image quality in Tissue Harmonic Imaging as compared to conventional ultrasound technique in abdominal and pelvic ultrasonography

Comparison of total image quality in Tissue Harmonic Imaging as compared to conventional ultrasound technique in abdominal and pelvic ultrasonography

An Adaptive Synthetic Aperture Method Applied to Ultrasound Tissue Harmonic Imaging.

In recent years, the minimum variance (MV) beamformer has been highly regarded since it provides high resolution and contrast in B-mode ultrasound imaging compared with nonadaptive delay-and-sum (DAS) beamformer. However, the performance of MV beamformer is degraded in the presence of the noise due to inaccurate estimation of the covariance matrix resulting in low-quality images. The conventional tissue harmonic imaging (THI) offers multiple advantages over conventional pulse-echo ultrasound imaging, including enhanced contrast resolution and improved axial and lateral resolutions, but low signal-to-noise ratio (SNR) is a major problem facing this imaging method, which uses a fixed transmit focus and dynamic receive focusing (DRF). In this paper, a synthetic aperture method based on the virtual source, namely, bidirectional pixel-based focusing (BiPBF), has been combined with the MV beamformer and then applied to second-harmonic ultrasound imaging. The main objective is suppressing the noise level to enhance the performance of the MV beamformer in the harmonic imaging, especially in lower and deeper depths where the SNR is low. In addition, combining the BiPBF and MV weighting results in simultaneous improvement in imaging resolution and contrast, in comparison with the conventional methods: DRF (DAS), BiPBF (DAS), and DRF (MV). The performance of the proposed method is evaluated on simulated and experimental RF data. The THI is achieved using the pulse-inversion technique. The results of the simulated wire phantom demonstrate that the proposed beamformer can achieve the best lateral resolution, along different depths, compared with DRF (DAS), BiPBF (DAS), and DRF (MV) methods. The results of the simulated and experimental cyst phantoms show that the new beamformer improves the contrast ratio (CR) and contrast-to-noise ratio (CNR) of the resulting images. In results of simulated cyst phantom, in average, the new beamformer improves the CR and CNR of the cyst about (7.4 dB, 49%), (3.2 dB, 16%), and (5 dB, 26%) compared with DRF (DAS), BiPBF (DAS), and DRF (MV), respectively. In results of experimental cyst phantom, these relative improvements are about (4.2 dB, 22%), (1.7 dB, 7%), and (2.6 dB, 15%). In addition, BiPBF (MV) method offers improved edge definition of cysts in comparison with the other methods.

Experimental evaluation of ultrasound higher-order harmonic imaging with Filtered-Delay Multiply And Sum (F-DMAS) non-linear beamforming

Tissue Harmonic Imaging (THI) mode is currently one of the preferred choices by the clinicians for its ability to provide enhanced ultrasound images, thanks to the use of the second harmonic component of backscattered echoes. This paper aims at investigating whether the combination of THI with Filtered-Delay Multiply And Sum (F-DMAS) beamforming can provide further improvements in image quality. F-DMAS is a new non-linear beamformer, which, similarly to THI, is based on the use of the second harmonics of beamformed signals and is known to increase image contrast resolution and noise rejection. Thus, we have first compared the images obtained by using F-DMAS and the standard Delay And Sum (DAS) beamformers when only the second harmonics of the received signals was selected. Moreover, possible improvements brought about by other harmonic components generated by the combined use of the fundamental plus second harmonics and F-DMAS beamforming have been explored. Experimental results demonstrate that, as compared to standard harmonic imaging with DAS, THI and F-DMAS can be joined to improve the −20 dB lateral resolution up to 1 mm, the contrast ratio up to 12 dB on a cyst-phantom and up to 9 dB on in vivo images.

Ultrasound Tissue Harmonic Imaging based on Wavelet Correlation Analysis

In this paper, an ultrasound tissue harmonic imaging method based on wavelet transform has been proposed. Wavelet transform is utilized to analyze the correlation between mother wavelet and the received echoes. In order to obtain a better correlation, a new mother wavelet named ‘Tissue wavelet’ is constructed according to the KZK equation. The proposed method was validated by experiments performed on an ultrasound flow phantom. Results showed that the contrast and axial resolution have been improved effectively.