Value of tissue harmonic imaging (THI) and contrast harmonic imaging (CHI) in detection and characterisation of breast tumours

Ultrasound-New Techniques Are Extending the Applications

BACKGROUND

Sonography is often the first imaging procedure to be used in diagnostic investigation of the abdomen. The aim of this article is to provide a new interdisciplinary overview of recent groundbreaking advances in this modality.

METHODS

A selective survey of the literature in PubMed was conducted. The literature search was carried out in 2021-2022 and included publications over the period 2004-2022.

RESULTS

The novel sonographic software techniques can be divided into algorithms that deal with conventional B-scan optimization and new programs that extend the scope of sonographic examination. The latter include elastography, contrast-enhanced sonography, and image fusion in combination with other cross-sectional imaging modalities. Elastography can be used to assess the presence of steatosis, fibrosis, or cirrhosis in patients with liver disease. One study reported diagnostic accuracy of 84-87% for the diagnosis of significant fibrosis (F2), 89-91% for the diagnosis of severe fibrosis (F3), and 92-93% for the diagnosis of liver cirrhosis (F4). Contrast-enhanced sonography is used for evaluation of tumors and trauma. A prospective multicenter study found sensitivity of 95.8% for the characterization of malignant lesions and specificity of 83.1% for benign lesions. Image fusion has the potential to improve the diagnostic assessment of parenchymatous organs, vascular conditions, and the prostate.

CONCLUSION

With continuous improvement of the B-scan and the development of high-frequency probes and novel investigation techniques, sonography has become established as an increasingly autonomous examination procedure.

Surface imaging of breast implants using modern high-frequency ultrasound technology in comparison to high-end sonography with power analyses for B-scan optimization1

AIM

This study aims to evaluate optimized breast implant surface-structure analysis by comparing high-end ultrasound technology with a new high frequency technique. This comparative study used new breast implants with different surfaces in an in vitro setting.

METHODS

Nine idle silicon or polyurethane (PU) breast implants were examined by two investigators in an experimental in vitro study using two high-end ultrasound devices with multi-frequency transducers (6-15 MHz, 9-16 MHz, 12.5-33 MHz).The ultrasound B-Mode was optimized using tissue harmonic imaging (THI), speckle reduction imaging (SRI, level 0-5), cross beam (high, medium, low) and photopic.Using a standardized ultrasound protocol, the implants were examined in the middle (point of highest projection) and lateral, by two independent examiners.Image evaluation was performed on anonymized digital images in the PACS. The aim was to achieve an artifact-free recording of the surface structure, the surface coating, the total image structures and, as far as possible, an artifact-free internal representation of the implants.For independent surface evaluation a score was used (0 = undetectability of surface structures, rich in artifacts, 5 = best possible, artifact free image quality).

RESULTS

The quality of ultrasound imaging of breast implant surfaces after the optimization of B-Scan differed significantly comparing high-end ultrasound technology with modern high-frequency ultrasound technology (p < 0,05).The following setting has been found to be the best setting with the highest image quality:B-Mode, SRI value 3, Crossbeam high level with color coded imaging for B- mode. In the total examined frequency range of 6-33 MHz, the highest image quality was found in the average frequency range of 12.5-33 MHz at both measured points. For both devices, device 1 (high-end) and device 2 (high frequency) ultrasound, the image quality was in the12.5-33 MHz frequency range with an average image quality of 3.236. It was significantly higher, than in the lower frequency ranges and the same frequency range with THI. (p < 0,05).  The image quality of the high-end sonography device was superior to the conventional high-frequency ultrasound device in all frequency ranges.

CONCLUSION

High-end ultrasound imaging technology was superior in the quality of implant surface evaluation in comparison to high-frequency ultrasound sonography. The gained knowledge can serve as a basis for further multicenter clinical application and studies with the aim to develop an objective, precise tool to evaluate the implant and the surrounding tissue with ultrasound.

Recent advances in X-ray imaging of breast tissue: From two- to three-dimensional imaging

Breast cancer is a globally widespread disease whose detection has already been significantly improved by the introduction of screening programs. Nevertheless, mammography suffers from low soft tissue contrast and the superposition of diagnostically relevant anatomical structures as well as from low values for sensitivity and specificity especially for dense breast tissue. In recent years, two techniques for X-ray breast imaging have been developed that bring advances for the early detection of breast cancer. Grating-based phase-contrast mammography is a new imaging technique that is able to provide three image modalities simultaneously (absorption-contrast, phase-contrast and dark-field signal). Thus, an enhanced detection and delineation of cancerous structures in the phase-contrast image and an improved visualization and characterization of microcalcifications in the dark-field image is possible. Furthermore, latest studies about this approach show that dose-compatible imaging with polychromatic X-ray sources is feasible. In order to additionally overcome the limitations of projection-based imaging, efforts were also made towards the development of breast computed tomography (BCT), which recently led to the first clinical installation of an absorption-based BCT system. Further research combining the benefits of both imaging technologies is currently in progress. This review article summarizes the latest advances in phase-contrast imaging for the female breast (projection-based and three-dimensional view) with special focus on possible clinical implementations in the future.

"I can see clearly now." fundamentals of breast ultrasound optimization

Unlike other modalities in breast imaging, breast ultrasound is very operator dependent. Proper characterization and management of breast lesions depends on the knowledge and skill of the radiologist performing the exam. Breast ultrasound optimization continues to evolve as the technology of ultrasound machines improves. The American College of Graduate Medical Education (ACGME) program requirements for graduate medical education in diagnostic radiology recently updated requirements to include competency in ultrasound physics, knobology, and image generation. As trainees are held to high ultrasound optimization standards, practicing radiologists who perform breast ultrasound exams must keep up to date on current breast ultrasound optimization techniques to avoid mischaracterizing and mismanaging breast ultrasound findings. In this paper, ultrasound optimization techniques, including patient positioning, transducer frequency, transducer contact and pressure, depth, gain, focus, tissue harmonic imaging, spatial compounding, dynamic range, speed of sound imaging, Doppler evaluation, and elastography will be described. Multiple ultrasound case examples will be used to illustrate application of these skills. After reading this paper, the reader will be able to apply these techniques to their own breast ultrasound practice, improving characterization and management of breast lesions in their patients.

Up-to-date Doppler techniques for breast tumor vascularity: superb microvascular imaging and contrast-enhanced ultrasound

Ultrasonographic Doppler techniques have improved greatly over the years, allowing more sophisticated evaluation of breast tumor vascularity. Superb microvascular imaging (SMI) and contrast-enhanced ultrasound (CEUS) with second-generation contrast agents are two representative up-to-date techniques. SMI is a sensitive Doppler technique that adopts an intelligent filter system to separate low-flow signals from artifacts. With the development of second-generation contrast agents, CEUS has also emerged as a useful Doppler technique for evaluating tumor microcirculation. Both techniques can improve the diagnostic performance of gray-scale ultrasonography by providing vascular information useful not only for the morphologic assessment of microvessels, but also for the quantitative analysis of perfusion. In this review, we explain the imaging principles and previous research underlying these two vascular techniques, and describe our clinical experiences.

X-ray phase-contrast imaging of the breast--advances towards clinical implementation

Breast cancer constitutes about one-quarter of all cancers and is the leading cause of cancer death in women. To reduce breast cancer mortality, mammographic screening programmes have been implemented in many Western countries. However, these programmes remain controversial because of the associated radiation exposure and the need for improvement in terms of diagnostic accuracy. Phase-contrast imaging is a new X-ray-based technology that has been shown to provide enhanced soft-tissue contrast and improved visualization of cancerous structures. Furthermore, there is some indication that these improvements of image quality can be maintained at reduced radiation doses. Thus, X-ray phase-contrast mammography may significantly contribute to advancements in early breast cancer diagnosis. Feasibility studies of X-ray phase-contrast breast CT have provided images that allow resolution of the fine structure of tissue that can otherwise only be obtained by histology. This implies that X-ray phase-contrast imaging may also lead to the development of entirely new (micro-) radiological applications. This review provides a brief overview of the physical characteristics of this new technology and describes recent developments towards clinical implementation of X-ray phase-contrast imaging of the breast.

[Latest developments in ultrasound of the liver]

Abdominal ultrasound (US) is often the first-line imaging modality used to assess focal liver lesions. Due to various new gray-scaled US techniques, such as tissue harmonic imaging (THI), spatial compounding technique and speckle reduction technique, as well as contrast-enhanced techniques, abdominal ultrasound nowadays has great potential regarding detection and characterization of focal liver lesions. Furthermore, image fusion with computed tomography (CT), magnetic resonance imaging (MRI) and 3D ultrasound will most likely help to improve clinical management before and after interventional procedures. This article illustrates the principles and clinical impact of recently developed techniques in the field of ultrasound.

[Modern gray-scale sonography of the breast]

Recently, the diagnosis of breast diseases by ultrasound has changed radically. It is no longer a complementary modality to mammography but a separate method to investigate breast disease. Innovative high-resolution ultrasound allows more specific diagnosis of breast tumors. Tissue-harmonic imaging not only uses the transmitted, fundamental frequency to obtain an image but also the harmonic frequency. The harmonic signal is processed by the ultrasound system with the result of better delineation of tissue structures and spatial compounding assembles an image from multiple images taken from different angles of echo waves. The effect is the reduction of artifacts with optimized contrast. Finally the advanced speckle reduction technique is used to smooth and homogenize the image. Additionally continuous advancement of new high-resolution linear transducers is responsible for the essential improvement of image quality. In conclusion, it is recommended to integrate all of the described modalities in order to obtain diagnostically conclusive image quality. This article demonstrates the new techniques and applications exemplified using images.

[Modern sonography in the diagnosis of acute abdomen]

Acute abdomen is a serious clinical situation and prompt imaging is mandatory so that appropriate therapeutic measures can be taken. Multiple diseases can present with the clinical signs and symptoms of acute abdomen. Ultrasound is widely available and can be performed expeditiously. Recently, major technical innovations in ultrasound technology were introduced which greatly enhanced the diagnostic accuracy in the evaluation of acute abdomen. Contrast-enhanced ultrasound is among these valuable innovations. In this article the application of modern ultrasound techniques for the diagnosis of the most common causes of acute abdomen is outlined, which may be due to diseases of the gastro-intestinal tract, parenchymal organs in the upper abdomen as well as vascular disorders. Moreover, the diagnostic efficacy and the value as compared to other imaging modalities are analyzed.

[Current developments in vascular ultrasound]

Ultrasound plays a central role in the diagnostic imaging of venous and arterial vessels, especially for the assessment or exclusion of arteriosclerotic vessel obstructions as well as venous or arterial thrombosis. Due to its excellent patient acceptance and its broad availability, ultrasound is considered the standard method of choice for vascular imaging. New techniques and methods have greatly enhanced its diagnostic accuracy, the most notable of which are the B-flow technique, a variant of Doppler signal read-out for reduction of artifacts in duplex sonography, as well as other techniques, such as tissue harmonic imaging, the cross-beam technique and the speckle-reduction technique, which employ different echo processing methods for contrast improvement and enhanced delineation of body structures adjacent to the vessels. The introduction of contrast enhanced ultrasound represents an important advancement and has brought a substantial improvement in sensitivity. This article describes and discusses these new techniques and methods of vascular ultrasound diagnostics with respect to their diagnostic value.

Contrast-enhanced ultrasound in the characterisation of breast masses: utility of quantitative analysis in comparison with MRI

OBJECTIVE

To evaluate the reliability of contrast-enhanced ultrasound quantitative analysis (CE-US) in characterizing breast lesions, in comparison with MRI.

MATERIALS

Thirty-nine patients with breast lesions BI-RADS 3-5 at US or mammography underwent CE-US and MRI. All lesions underwent histological and quantitative enhancement evaluation with both imaging methods. B-mode US, colour/power Doppler US and CE-US were used; an amplitude and phase modulation technique (CPS) read the signals produced by microbubbles and dedicated software produced the following parameters on time/intensity (T/I) curves: peak %, time to peak (TTP), mean transit time (MTT), regional blood volume (RBV) and regional blood flow (RBF). Student's t test was used to calculate the diagnostic accuracy of CE-US parameters compared with histological results. MRI (1.5 T) was performed before and after bolus gadolinium enhancement. Time/intensity curves were generated for all nodules and Fischer's multimodal score was used to classify them.

RESULTS

Pathology showed 43 nodules (11 benign; 32 malignant). Peak and RBF were the most significant parameters in differential diagnosis, with p values of 0.02 and 0.004, respectively. Positive predictive value (PPV) of CE-US evaluation was 91%, negative predictive value (NPV) was 73% with a high concordance index (k = 0.59) with MRI.

CONCLUSIONS

CE-US quantitative analysis offers an objective and reproducible assessment of lesion vascularisation, with good correlation with the results of MRI.

Delta-projection imaging on contrast-enhanced ultrasound to quantify tumor microvasculature and perfusion

RATIONALE AND OBJECTIVES

The aim of this study was to assess the Delta-projection image processing technique for visualizing tumor microvessels and for quantifying the area of tissue perfused by them on contrast-enhanced ultrasound images.

MATERIALS AND METHODS

The Delta-projection algorithm was implemented to quantify perfusion by tracking the running maximum of the difference (Delta) between the contrast-enhanced ultrasound image sequence and a baseline image. Twenty-five mice with subcutaneous K1735 melanomas were first imaged with contrast-enhanced grayscale and then with minimum-exposure contrast-enhanced power Doppler (minexCPD) ultrasound. Delta-projection images were reconstructed from the grayscale images and then used to evaluate the evolution of tumor vascularity during the course of contrast enhancement. The extent of vascularity (ratio of the perfused area to the tumor area) for each tumor was determined quantitatively from Delta-projection images and compared to the extent of vascularity determined from contrast-enhanced power Doppler images. Delta-projection and minexCPD measurements were compared using linear regression analysis.

RESULTS

Delta-projection was successfully performed in all 25 cases. The technique allowed the dynamic visualization of individual blood vessels as they filled in real time. Individual tumor blood vessels were distinctly visible during early image enhancement. Later, as an increasing number of blood vessels were filled with the contrast agent, clusters of vessels appeared as regions of perfusion, and the identification of individual vessels became difficult. Comparisons were made between the perfused area of tumors in Delta-projections and in minexCPD images. The Delta-projection perfusion measurements were correlated linearly with minexCPD.

CONCLUSION

Delta-projection visualized tumor vessels and enabled the quantitative assessment of the tumor area perfused by the contrast agent.

[US and dense breasts: where do we stand?]

The use of ultrasonography in dense breast remains a controversial topic. It is acknowledged that ultrasound as an adjunct to mammography increases the detection rate of breast cancers. However, the main limitation of US, in addition to its operator dependent nature, is its low specificity, leading to a high rate of false positive results. Several techniques can be used to improve the performance of US and cost/effectiveness ratio, such as Doppler imaging, harmonic imaging, spatial and frequency compound imaging, all of which are routinely available, and elastosonography, contrast US and 3D US which are still in development.

[Modern ultrasound diagnostics of deep vein thrombosis in lung embolism of unknown origin]

PURPOSE

We compared innovative ultrasound techniques such as tissue harmonic imaging (THI) and cross-beam technique with speckle reduction imaging (SRI) to conventional fundamental B scan in the diagnosis of deep vein thrombosis.

MATERIAL AND METHODS

We investigated a total number of 185 patients with clinical symptoms of acute vein thrombosis. We documented the thrombosis in the patients using multifrequency ultrasound probes (5-7 MHz, 6-9 MHz, 9-14 MHz, Logig 9, GE) and recorded ultrasound sequences in fundamental B scan, THI, and cross-beam technique with SRI (grade 2). Three blinded ultrasound investigators ranked the marking of the thrombosis in each of these image modalities and graded them with the numbers 5 = weak, 4 = moderate, 3 = satisfactory, 2 = good, and 1 = excellent. We calculated the median and a t-test for each of these image modalities.

RESULTS

We diagnosed 115 thromboses (62%) in 185 investigated patients. This group could be divided as follows: 11 patients (6%) with three-level thrombosis, 37 patients (20%) with two-level thrombosis, and 67 (36%) with one-level thrombosis. The one-level thrombosis group included five (3%) patients with muscle vein thromboses, seven (4%) cases of thrombophlebitis without involvement of the deep vein system, and three (2%) cases of thrombophlebitis with involvement of the deep vein system. The t-test for unconnected samples showed significant differences (p <0.05) in iliac veins and highly significant differences (p <0.001) in the veins of the lower extremity due to the superior capabilities for detection of thrombosis using the cross-beam technique with SRI compared to THI and the fundamental B scan.

CONCLUSION

The use of high-resolution linear ultrasound probes with the concomitant application of THI and cross-beam technique with SRI facilitates the diagnosis of deep vein thrombosis. The employment of these new ultrasound modalities is an advantage in distinguishing the veins from the surrounding tissue structures and helps in evaluating the compressibility of venous vessels.