Quantifying Image Quality Improvement Using Elevated Acoustic Output in B-Mode Harmonic Imaging

Feasibility and accuracy of left ventricular volumes and ejection fraction determination by fundamental, tissue harmonic, and intravenous contrast imaging in difficult-to-image patients

ObjectiveTo determine the usefulness of tissue harmonic imaging (THI) and pulse-inversion harmonic imaging (PIHI) in the evaluation of normal and abnormal fetuses.Materials and MethodsForty-one pregnant women who bore a total of 31 normal and ten abnormal fetuses underwent conventional ultrasonography (CUS), and then THI and PIHI. US images of six organ systems, namely the brain, spine, heart, abdomen, extremities and face were compared between the three techniques in terms of overall conspicuity and the definition of borders and internal structures.ResultsFor the brain, heart, abdomen and face, overall conspicuity at THI and PIHI was significantly better than at CUS (p < 0.05). There was, though, no significant difference between THI and PIHI. Affected organs in abnormal fetuses were more clearly depicted at THI and PIHI than at CUS.ConclusionBoth THI and PIHI appear to be superior to CUS for the evaluation of normal or abnormal structures, particularly the brain, heart, abdomen and face.

New concept in echocardiography: harmonic imaging of tissue without use of contrast agent

Tissue harmonic imaging is a new ultrasound imaging technique which uses the harmonic components generated by non-linear acoustic propagation through human tissues to form an image. Several factors affect tissue harmonic imaging image quality. First, strong suppression of the fundamental frequency is necessary to allow the full dynamic range of the harmonic signals to appear. Second, the harmonic components should be enhanced when they are much weaker than the fundamental frequency. In this research, based on tissue harmonic imaging, a new technique for enhancing the ultrasound imaging is presented. We first theoretically prove obtaining and enhancing the fourth harmonic and suppressing the fundamental frequency, second and third harmonics, and then after simulation of the theory by MATLAB 7·1 software, we show that our method can enhance the ultrasound image quality.

Coded Tissue Harmonic Ultrasound of Focal Hepatic Lesions: Comparison of Image Quality with Conventional Ultrasound

Reduction of stent artifacts using high-frequency harmonic ultrasound imaging

To assess the guidance of tissue harmonic imaging (THI) and contrast harmonic imaging (CHI) for vacuum assisted biopsies of suspicious breast lesions compared to fundamental B-mode ultrasound-guided biopsies. In 550 patients, ultrasound examinations of the breast were performed prospectively using fundamental B-scan, THI, and CHI. Focal lesions were documented in comparable projections for all three ultrasound modes. As contrast agent, a dose of 0.5 milliliters of Perflutren Protein-Type A microspheres ( Optison) was injected. An ultrasound-guided biopsy was performed in 38 focal lesions. Three radiologists experienced in breast imaging retrospectively assessed the lesions on the ultrasound images. Thirty-eight suspicious focal lesions [size 4 - 15 mm; median 8 mm] were detected by ultrasound. Of these, 29 were detected by fundamental B-scan images, 34 by THI, and 38 by CHI. Ultrasound-guided biopsy was performed on all of these lesions. No complications related to the biopsy were observed. In 25/38 cases, invasive carcinomas were found; in 6/38 ductal carcinomas in situ; in 3 cases metastases of already known invasive ductal carcinomas; and in 4 cases fibroadenomas. The size of the lesion was best identified using THI, smaller lesions (< 10 mm) using CHI. THI and CHI can help to detect focal lesions in dense breasts. Both modes can make it easier to perform ultrasound-guided biopsies of focal breast lesions.

BackgroundIncreased subcutaneous fat thickness and depth of target organs in over-obese patients, results in weak signals and inadequate images. Tissue harmonic imaging has been used widely in obese patients and is believed to result in higher quality images. This superiority is not proved in modern machines with improved image quality in conventional mode.ObjectiveTo compare the image quality between conventional and tissue harmonic ultrasound images.MethodsThis cross-sectional study was carried out from March 2015 to June 2016. Seventy-six over-obese patients referred to Ghaem Hospital (Mashhad, Iran) for weight-correction surgeries, were enrolled into the study. Conventional and tissue harmonic images of their kidneys were blinded and compared back-to-back by four expert radiologists. Data were analyzed by SPSS version 16, using Cochrane’s Q test.ResultsAll raters reported image quality to be better in tissue harmonic compared to fundamental frequency ultrasound (p=0.000, Cochrane’s Q test). Although better image quality in tissue harmonic mode was reported by the four raters, there was weak inter-observer agreement (p=0.081 for right kidney and p=0.21 for left kidney).ConclusionAdvances in ultrasound equipment and the introduction of tissue harmonic imaging can improve the diagnostic performance in over-obese patients and this mode of imaging should be used whenever evaluating over-obese subjects.

Qualitative and quantitative effects of harmonic echocardiographic imaging on endocardial edge definition and side-lobe artifacts

High-grade Video Compression of Echocardiographic Studies: A Multicenter Validation Study of Selected Motion Pictures Expert Groups (MPEG)-4 Algorithms

Wall motion score index (WMSI) is an important prognostic indicator in heart failure (HF) patients but requires endocardial visualisation. This study evaluated the role tissue harmonic imaging (THI) and contrast opacification (LVO) for improving endocardial visualisation and the determination of WMSI in HF patients. Thirty-one HF patients and 30 controls underwent apical echocardiography with fundamental imaging (FUND), THI and THI with contrast agent (Levovist). Visualisation and motion were graded in the six segments from each of the apical two and four chamber views. Both THI and LVO reduced the percentage of non-visualised segments (FUND 13.6%, THI 5.6%, LVO 2.8%, p=0.01) in the controls, but in HF patients, only THI improved visualisation (% segments not visualised FUND 9.7%, THI 3.5%, LVO 4.8%, p=0.06). The anterior and lateral walls were the least well visualised with FUND, but improved with LVO (anterior p=0.0026, lateral p=0.0003). No improvement was seen in the inferior wall (p=0.30) or septum (p=0.2). WMSI was similar by all methods and negatively correlated with ejection fraction (FUND r=-0.69, THI r=-0.74, LVO r=-0.77, all p<0.001). THI improved endocardial visualisation in all subjects and LVO offered additional benefit in the controls, but not in HF patients. Regional endocardial visualisation was inconsistent. Thus, both patient factors and wall segment site need to be considered when using contrast agents for endocardial visualisation.

Tissue Harmonic Imaging (THI) is an invaluable tool in clinical ultrasound owing to its enhanced contrast resolution and reduced reverberation clutter in comparison to fundamental mode imaging. However, harmonic content separation based on high pass filtering suffers from potential contrast degradation or lower axial resolution due to spectral leakage. Whereas nonlinear multi-pulse harmonic imaging schemes, such as amplitude modulation and pulse inversion, suffer from a reduced framerate and comparatively higher motion artifacts due to the necessity of at least two pulse echo acquisitions. To address this problem, we propose a deep-learning-based single-shot harmonic imaging technique capable of generating comparable image quality to pulse amplitude modulation methods, yet at a higher framerate and with fewer motion artifacts. Specifically, an asymmetric convolutional encoder-decoder structure is designed to estimate the combination of the echoes resulting from the half-amplitude transmissions using the echo produced from the full amplitude transmission as input. The echoes were acquired with the checkerboard amplitude modulation technique for training. The model was evaluated across various targets and samples to illustrate generalizability as well as the possibility and impact of transfer learning. Furthermore, for possible interpretability of the network, we investigate if the latent space of the encoder holds information on the nonlinearity parameter of the medium. We demonstrate the ability of the proposed approach to generate harmonic images with a single firing that are comparable to those from a multi-pulse acquisition.

Stress echocardiography is used to detect myocardial ischemia by evaluating cardiovascular function both at rest and at elevated heart rates. Stress echocardiography requires excellent visualization of the left ventricle (LV) throughout the cardiac cycle. However, LV endocardial border visualization is often negatively impacted by high levels of clutter associated with patient obesity, which has risen dramatically worldwide in recent decades. Short-lag spatial coherence (SLSC) imaging has demonstrated reduced clutter in several applications. In this work, a computationally efficient formulation of SLSC was implemented into an object-oriented graphics processing unit-based software beamformer, enabling real-time (>30 frames per second) SLSC echocardiography on a research ultrasound scanner. The system was then used to image 15 difficult-to-image stress echocardiography patients in a comparison study of tissue harmonic imaging (THI) and harmonic spatial coherence imaging (HSCI). Video clips of four standard stress echocardiography views acquired with either THI or HSCI were provided in random shuffled order to three experienced readers. Each reader rated the visibility of 17 LV segments as "invisible," "suboptimally visualized," or "well visualized," with the first two categories indicating a need for contrast agent. In a symmetry test unadjusted for patientwise clustering, HSCI demonstrated a clear superiority over THI ( ). When measured on a per-patient basis, the median total score significantly favored HSCI with . When collapsing the ratings to a two-level scale ("needs contrast" versus "well visualized"), HSCI once again showed an overall superiority over THI, with by McNemar test adjusted for clustering.

To evaluate the role of tissue harmonic imaging (THI) in acute pancreatitis, and to compare its findings with conventional grey-scale sonography and contrast-enhanced computed tomography (CECT) scan, we evaluated 25 patients diagnosed with acute pancreatitis on clinical examination and laboratory findings. Conventional grey-scale ultrasound followed by tissue harmonic sonography was done on the same machine followed by a CECT within 12 h of the ultrasound examination. The present study showed that sonograms obtained with THI were of much better quality than those obtained conventionally, especially for the pancreatic tail. The benefits of harmonic imaging were more apparent in obese patients and in others whose body habitus was unfavourable for sonography. In the assessment of pancreatic image quality, grey-scale imaging had an accuracy of 60, 80 and 28% in relation to the head, body and tail, respectively. In comparison, THI had a far higher accuracy of 80, 92 and 60% in relation to the head, body and tail, respectively, with the superiority being most obvious in the pancreatic tail region. There were no cases in which tissue harmonic sonography provided less information than conventional sonography. However, CECT scan remained the best modality in all patients for the evaluation of acute pancreatitis. It showed superior demonstration of all the morphological changes, ranging from minimal pancreatic oedema to extensive fluid collections, necrosis and the haemorrhage that developed in fulminant severe pancreatitis. Our experience thus suggests that THI cannot replace CT scan as the gold standard in the assessment of acute pancreatitis, as it is poor in evaluating the pancreatic tail, cannot clearly distinguish phlegmon from necrosis, and is inferior to CT in the assessment of the complications of acute pancreatitis.

This article gives an overview of the technical possibilities and clinical applications of modern ultrasound. B-mode and Doppler imaging are already essential in daily routine. Advanced technology, such as harmonic imaging, improves image quality. Tissue harmonic imaging provides better resolution by reducing noise, whereas the introduction of contrast agents increases the perceptibility of focal lesions, e.g., liver tumors. Meanwhile the diagnostic accuracy of contrast-enhanced ultrasound imaging is comparable with CT imaging. Other tools, e.g., elastography, ameliorate the detection of liver fibrosis and tumors. Currently, application of three-dimensional and four-dimensional imaging is of low clinical relevance. Panoramic imaging provides images close to CT or MRI.