Ultrasound imaging in three and four dimensions

Spatial lung imaging in clinical and translational settings

For many severe lung diseases, non-invasive biomarkers from imaging could improve early detection of lung injury or disease onset, establish a diagnosis, or help follow-up disease progression and treatment strategies. Imaging of the thorax and lung is challenging due to its size, respiration movement, transferred cardiac pulsation, vast density range and gravitation sensitivity. However, there is extensive ongoing research in this fast-evolving field. Recent improvements in spatial imaging have allowed us to study the three-dimensional structure of the lung, providing both spatial architecture and transcriptomic information at single-cell resolution. This fast progression, however, comes with several challenges, including significant image file storage and network capacity issues, increased costs, data processing and analysis, the role of artificial intelligence and machine learning, and mechanisms to combine several modalities. In this review, we provide an overview of advances and current issues in the field of spatial lung imaging.

Three-dimensional sonography has satisfied accuracy for detecting rotator cuff tears

Background

Rotator cuff injuries and tears are common causes of shoulder pain and dysfunction, necessitating accurate diagnostic methods to guide clinical decision-making. This study evaluates the diagnostic utility of three-dimensional (3D) shoulder sonography in identifying rotator cuff injury and tear patterns.

Methods

A comprehensive search across seven electronic databases, which included Cochrane Library, Embase, PubMed, Cochrane Library, China Biology Medicine (CBM) database, CNKI, Wanfang, and VIP database. These databases were utilized to retrieve articles that assess the diagnostic value of 3D shoulder sonography for identifying rotator cuff injuries and tear patterns. The effectiveness of 3D shoulder sonography was assessed in terms of sensitivity, specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR), and diagnostic odds ratio (DOR). For each parameter, the 95% confidence intervals were calculated. Additionally, summary receiver operating characteristic curves (SROCs) were constructed, allowing for a comprehensive evaluation of diagnostic accuracy, which is reflected in the area under the SROC curve (AUC).

Results

Screening of 8,508 identified nine literatures eligible for inclusion in the meta-analysis, encompassing a total of 366 patients. The analysis of detecting any rotator cuff tear revealed a sensitivity of 0.97 and specificity of 0.87, yielding a DOR of 90.03 and an AUC of 0.98. Furthermore, 3D shoulder sonography demonstrated satisfactory accuracy in detecting both full and partial-thickness rotator cuff tears (Sensitivity: 0.92 vs. 0.83, specificity: 0.94 vs. 097, and AUC: 0.96 vs. 0.95).

Conclusion

This study indicates that three-dimensional sonography has satisfied accuracy for detecting rotator cuff tears.

Freehand 3-D Ultrasound Imaging: A Systematic Review

Two-dimensional ultrasound (US) imaging has been successfully used in clinical applications as a low-cost, portable and non-invasive image modality for more than three decades. Recent advances in computer science and technology illustrate the promise of the 3-D US modality as a medical imaging technique that is comparable to other prevalent modalities and that overcomes certain drawbacks of 2-D US. This systematic review covers freehand 3-D US imaging between 1970 and 2017, highlighting the current trends in research fields, the research methods, the main limitations, the leading researchers, standard assessment criteria and clinical applications. Freehand 3-D US systems are more prevalent in the academic environment, whereas in clinical applications and industrial research, most studies have focused on 3-D US transducers and improvement of hardware performance. This topic is still an interesting active area for researchers, and there remain many unsolved problems to be addressed.

Imaging in percutaneous nephrolithotomy

Image guidance is a critical factor for the performance of urologic interventions. Percutaneous minimally invasive procedures have been developed and are being used with constantly increasing frequency. Procedures such as percutaneous nephrolithotomy (PCNL) are not performed without any image guidance. Recent developments in medical imaging, such as three-dimensional radiographic fluoroscopy, CT, and magnetic resonance (MR) fluoroscopy, four-dimensional ultrasonography, and image fusion techniques, propose a new generation of image-guidance tools that promise to improve patient care. These developments have been used or have the potential to be used in PCNL and other urologic interventional procedures. Moreover, advanced needles and needle guidance systems provide a new perspective for the nephrolithotomy suite of the future. The current review presents existing imaging technology in PCNL and interventional urology as well as advanced imaging techniques that are being or are expected to be evaluated in PCNL practice.

Computational cardiac atlases: from patient to population and back

Integrative models of cardiac physiology are important for understanding disease and planning intervention. Multimodal cardiovascular imaging plays an important role in defining the computational domain, the boundary/initial conditions, and tissue function and properties. Computational models can then be personalized through information derived from in vivo and, when possible, non-invasive images. Efforts are now established to provide Web-accessible structural and functional atlases of the normal and pathological heart for clinical, research and educational purposes. Efficient and robust statistical representations of cardiac morphology and morphodynamics can thereby be obtained, enabling quantitative analysis of images based on such representations. Statistical models of shape and appearance can be built automatically from large populations of image datasets by minimizing manual intervention and data collection. These methods facilitate statistical analysis of regional heart shape and wall motion characteristics across population groups, via the application of parametric mathematical modelling tools. These parametric modelling tools and associated ontological schema also facilitate data fusion between different imaging protocols and modalities as well as other data sources. Statistical priors can also be used to support cardiac image analysis with applications to advanced quantification and subject-specific simulations of computational physiology.

Advances in imaging for urologic procedures

Improvements in imaging and device engineering have led to the rapid development of advanced, minimally invasive techniques in urologic care. While imaging advances have had a major effect in the areas of diagnosis, surgical planning and therapeutic assessment, the focus of this Review is on developments in intraoperative imaging that are currently making an impact in urology and are likely to provide additional opportunities to urologists in the years to come. While previous image-guided urologic procedures have mostly utilized two-dimensional X-ray images, it is expected that new technologies will involve the use of three- and four-dimensional multi-modality imaging, molecular imaging, and robot-assisted image-guidance techniques. Application of these procedures will bring together the complementary disciplines of endourology and interventional radiology in the development of multidisciplinary, cooperative approaches to providing optimal treatments and outcomes for urologic disease.

Interventional procedures in superficial lesions: the value of 2D with additional coronal reformatted 4D ultrasonography guidance

Objective

We wanted to assess the usefulness of four-dimensional (4D) ultrasonography (US), i.e., real-time three-dimensional US, as an adjunct for performing various US-guided interventional procedures in superficial lesions.

Materials and Methods

Thirty-three patients were referred for US-guided interventional procedures for superficial lesions, including core biopsy in 19, fine-needle aspiration in eight, therapeutic drug injection in four and needle puncture in two. The procedures were performed under 4D US guidance. We reviewed the pathologic/cytologic results of the core biopsies or needle aspirations, and also the outcomes of drug injection or needle puncture.

Results

For all the patients who underwent 4D US-guided core biopsy, the specimens were adequate for making the pathological diagnosis, and specimens were successfully obtained for those patients who underwent 4D US-guided aspiration. The patients treated with 4D US-guided therapeutic drug injection or needle puncture had a good response. No major procedure-related complications occurred. The procedural times were similar to those procedural times with using two-dimensional US.

Conclusion

Combining the two dimensional and 4D US techniques aids the physician when performing US-guided interventional procedures for the superficial lesions.

Examination of the fetal brain by transabdominal three-dimensional ultrasound: potential for routine neurosonographic studies

OBJECTIVE

To evaluate the role of transabdominal three-dimensional (3D) ultrasound in the assessment of the fetal brain and its potential for routine neurosonographic studies.

METHODS

We studied prospectively 202 consecutive fetuses between 16 and 24 weeks' gestation. A 3D ultrasound volume of the fetal head was acquired transabdominally. The entire brain anatomy was later analyzed using the multiplanar images by a sonologist who was expert in neonatal cranial sonography. The quality of the conventional planes obtained (coronal, sagittal and axial, at different levels) and the ability of the 3D multiplanar neuroscan to visualize properly the major anatomical structures of the brain were evaluated.

RESULTS

Acceptable cerebral multiplanar images were obtained in 92% of the cases. The corpus callosum could be seen in 84% of the patients, the fourth ventricle in 78%, the lateral sulcus (Sylvian fissure) in 86%, the cingulate sulcus in 75%, the cerebellar hemispheres in 98%, the cerebellar vermis in 92%, the medulla oblongata in 97% and the cavum vergae in 9% of them. The thalami and the cerebellopontine cistern (cisterna magna) were identified in all cases. At or beyond 20 weeks, superior visualization (in > 90% of cases) was achieved of the cerebral fissures, the corpus callosum (97%), the supracerebellar cisterns (92%) and the third ventricle (93%). Some cerebral fissures were seen initially at 16-17 weeks.

CONCLUSION

Multiplanar images obtained by transabdominal 3D ultrasound provide a simple and effective approach for detailed evaluation of the fetal brain anatomy. This technique has the potential to be used in the routine fetal anomaly scan.

Ultrasonographic contrast media: has the time come in obstetrics and gynecology?

OBJECTIVE

The aim of this work was to review the technical aspects and clinical applications of contrast media (microbubbles and nanomolecular agents) in obstetric and gynecologic ultrasonographic imaging.

METHODS

With the use of a computerized database (MEDLINE) and several Web-based search engines (Google Scholar and Copernic), relevant articles on ultrasonographic contrast media were reviewed. References cited in these articles and not obtained via the search engines were also reviewed.

RESULTS

Ultrasonographic contrast media constitute a new and expanding technology. They are frequently used, for example, in adult cardiology. Extensive research in laboratory setups, animals, and human subjects has shown their safety and huge potential as an adjunctive tool in clinical practice. They increase signals returning from insonated tissues and are particularly effective as intravascular agents, enhancing color and Doppler signals, for instance. Preliminary results in tumor imaging are encouraging. The ultrasonographic contrast media permit pharmacokinetic perfusion studies, which may be of enormous clinical importance in the study of early cancer development. Targeted imaging and therapies are becoming a reality. Microbubbles have already brought a new dimension to diagnostic ultrasonographic imaging. Many authors have described the clinical value of these agents in liver, prostate, and breast imaging, among others. Newer types of media, the nanomolecules, are now emerging as the latest in imaging enhancers as well as therapeutic agent carriers.

CONCLUSIONS

Although showing potential in imaging of the uterus and fallopian tubes as well as some obstetric applications, the contrast media, in particular the nanomolecules, seem to be most promising in ovarian cancer.

Real time computation and temporal coherence of opacity transfer functions for direct volume rendering of ultrasound data

Opacity transfer function (OTF) generation for direct volume rendering of medical image data is an intensely discussed subject. Several automatic methods exist for CT and MRI data, which are not apt for ultrasound data, mainly due to its low signal-to-noise ratio. Furthermore, ultrasound (US) imaging is able to produce time-varying 3D datasets in real time thus opening the door to 4D visualization. However, OTF design for 4D datasets has not been exhaustively discussed until now. We present an efficient solution to generate an optimized OTF for a given 3DUS dataset in real time. Our method results in excellent visualization which we demonstrate using 3D fetus datasets. Finally, we discuss the applicability of our method to 4DUS visualization.

Three-Dimensional Ultrasound in Small Parts

For longer than 40 years, ultrasound (US) has been a widely used imaging tool in medical practice, which has proved helpful for the diagnosis and staging of diseases. Although three-dimensional ultrasound (3D) US has been available for more than 10 years, it was only through the development of the most recent computer technologies and its adaptation to ultrasound systems, that 3D US has become able to achieve the high level of sensitivity and performance necessary to be considered seriously in clinical practice. 3D US is rapidly turning into a technology with an ever-increasing range of applications in numerous fields because, among other reasons, it helps overcome some of the key limitations related to two-dimensional imaging. 3D US can be used in ultrasonography for small parts, among other medical areas. The assessment of the testicle, parotid, thyroid and parathyroid glands is properly achieved. The multiplanar presentation and niche mode are quite useful to determine the extension--inside or outside the organs-, of nodules, cysts or tumors. The volume measurement is better assessed with 3D US and given this, we can perform studies that follow growth in order to decide medical or surgical treatment. The VOCAL makes it possible to obtain a proper after-treatment follow-up of focal disorders in these small organs. Neovascularization is clearly viewed with 3D US and probably can suggest malignant origin of a neoplasm. 3D US offers a more comprehensive image of anatomical structures and pathological conditions and also permits to observe the exact spatial relationships. We are aware more studies are needed to demonstrate specificity and sensibility of 3D US in particular clinical conditions, not only in small parts but also is some other non-Ob/Gyn applications.

Musculoskeletal ultrasound--a state of the art review in rheumatology. Part 1: Current controversies and issues in the development of musculoskeletal ultrasound in rheumatology

As we begin the 21st century, musculoskeletal ultrasound (MSUS) is routinely used by an increasing number of rheumatologists throughout Europe and there is a growing interest in the application of MSUS in rheumatological practice in the UK. MSUS allows high-resolution, real-time imaging of articular and periarticular structures and has the advantages of being non-radioactive, inexpensive, portable, highly acceptable to patients and repeatable. There are a number of critical issues that need to be addressed in order to develop the role of MSUS within rheumatology. These include issues of equipment costs, training and certification and the relationship of rheumatologists and radiologists in advancing the field of MSUS. Rheumatologists must demonstrate the relevance of MSUS in their clinical practice through high-quality research. Emerging technologies such as power Doppler and 3D imaging will further improve imaging capabilities and the range of clinical applications of MSUS systems. This paper reviews how MSUS in rheumatology has evolved and the controversies and issues that rheumatologists must now address in developing MSUS as an indispensable, everyday clinical tool.

Something Old and Something New: a Brief History of Thyroid Ultrasound Technology

OBJECTIVE

To discuss both early and recent ultrasound technologic advances and to explore the role of such technology in the evaluation of the thyroid gland.

METHODS

The physics of sound and the history of the use of reflected sound waves are reviewed, and the medical applications of ultrasound, with a particular focus on the thyroid gland, are presented.

RESULTS

Since the first reports of thyroid ultrasonography were published in the late 1960s, the field has undergone remarkable evolution. Ultrasound imaging improved in parallel with growth in computing, transducer, and display technology. The transition from A-mode to B-mode to gray-scale imaging was associated with dramatic improvements in clarity and interpretability of ultrasound images. Current high-resolution ultrasound images are able to identify virtually all structural thyroid lesions of clinical significance. Although ultrasound characteristics cannot be used for accurate diagnosis of benign thyroid lesions, certain features such as irregular margins, microcalcifications, and central vascularity suggest the presence of "suspicious" thyroid nodules. Recent advances including the use of contrast agents, tissue harmonic imaging, and multiplanar reconstruction of images will further enhance the resolution and interpretability of ultrasound images. The use of Doppler flow analysis may improve the predictive value for determining the risk of a malignant thyroid lesion, but no current ultrasound technique is capable of determining benignity with an acceptable degree of accuracy. Ultrasound guidance of fine-needle aspiration biopsy has been demonstrated to improve both diagnostic yield and accuracy and will likely become the standard of care.

CONCLUSION

Because high-quality ultrasound systems are now available at a reasonable price, routine clinical use of ultrasonography is considered an important extension of the physical examination by many endocrinologists.

Ultrasonography in rheumatoid arthritis: a very promising method still needing more validation

PURPOSE OF REVIEW

Through recent technological advances, ultrasonography allows high-resolution visualization of inflammatory and destructive changes in the small superficial joints of hands and feet, and ultrasonography is increasingly used by rheumatologists for assessment of rheumatoid arthritis patients. It is, therefore, highly relevant to consider the validity of ultrasonographic measures of rheumatoid joint inflammation and damage.

RECENT FINDINGS

Organized by type of validity, data on ultrasonography in rheumatoid arthritis are reviewed. Encouraging reports of high agreement of ultrasonographic findings between observers, with MRI and, in knee and hip joints, histopathologic assessments were recently published. New quantitative and semiquantitative evaluation methods have been suggested, and the first systematic follow-up studies suggest an ability of ultrasonography to monitor joint inflammation and damage. However, a number of essential issues are still largely unexplored, including interscanner variability, sensitivity to change, prognostic value, and value in the diagnosis of rheumatoid arthritis. Suggested areas of priority in research and development of ultrasonography in rheumatoid arthritis are outlined.

SUMMARY

Ultrasonography is a very promising method in the assessment of rheumatoid arthritis joints, but still needs more validation before it can take up its expected role on a scientific basis as an important tool for diagnosis, monitoring, and prognostication of patients with rheumatoid arthritis and suspected rheumatoid arthritis.

Three-dimensional ultrasonography: an objective outcome tool to assess collagen distribution in women with stress urinary incontinence

OBJECTIVES

To examine the distribution of periurethral collagen by three-dimensional ultrasonography (3D US) and to incorporate this technology into a practical treatment decision tree for women with stress urinary incontinence desiring collagen injection.

METHODS

Forty-six women who received periurethral collagen injection were assessed with 3D US to document the position and volume of collagen around the urethra. Patients with a good clinical response were observed with serial 3D US scans. Women with no persistent improvement who showed a low volume or asymmetric distribution of collagen were offered repeat injections. When the patient had no improvement despite symmetric or circumferential distribution of collagen with good volume retention, another anti-incontinence treatment was recommended. Group 1 was composed of women who had a good clinical outcome and group 2 of those who did not. A statistical comparison between the two outcome groups was done to determine whether any particular distribution pattern was associated with an increased likelihood of clinical success.

RESULTS

Of the 46 patients, 21 (46%) were satisfied with their continence after their last periurethral collagen injection, with a median follow-up of 14.0 months (range 2 months to 4.25 years). A significantly greater proportion of patients in group 1 had circumferentially distributed collagen on 3D US compared with those in group 2 (62% versus 20%, P = 0.006).

CONCLUSIONS

Circumferential distribution of collagen around the urethra is associated with a higher likelihood of clinical success. The assessment of periurethral collagen by 3D US provides an affordable, noninvasive, objective outcome measure that may aid in treatment planning.

Advances in ultrasound

Ultrasound (US) has undergone dramatic changes since its inception three decades ago; the original cumbersome B-mode gantry system has evolved into a high resolution real-time imaging system. This review describes both recent advances in ultrasound and contrast media and likely future developments. Technological advances in electronics and computing have revolutionized ultrasound practice with ever expanding applications. Developments in transducer materials and array designs have resulted in greater bandwidths with improvements in spatial and contrast resolution. Developments in digital signal processing have produced innovations in beam forming, image display and archiving. Technological advances have resulted in novel imaging modes which exploit the non-linear behaviour of tissue and microbubble contrast agents. Microbubble contrast agents have dramatically extended the clinical and research applications of ultrasound. Not only can Doppler studies be enhanced but also novel non-linear modes allow vessels down to the level of the microcirculation to be imaged. Functional and quantitative studies allow interrogation of a wide spectrum of tissue beds. The advent of tissue-specific agents promises to improve the sensitivity and specificity of ultrasound in the detection and characterization of focal liver lesions to rival that of computed tomography (CT) and magnetic resonance imaging (MRI). Ultrasound has recently moved into therapeutic applications with high intensity focused ultrasound (HIFU) and microbubble assisted delivery of drugs and genes showing great promise.

Real-time spatial compound imaging: application to breast, vascular, and musculoskeletal ultrasound

Real-time spatial compound imaging (SonoCT) is an ultrasound technique that uses electronic beam steering of a transducer array to rapidly acquire several (three to nine) overlapping scans of an object from different view angles. These single-angle scans are averaged to form a multiangle compound image that is updated in real time with each subsequent scan. Compound imaging shows improved image quality compared with conventional ultrasound, primarily because of reduction of speckle, clutter, and other acoustic artifacts. Early clinical experience suggests that real-time spatial compound imaging can provide improved contrast resolution and tissue differentiation that is beneficial for imaging the breast, peripheral blood vessels, and musculoskeletal injuries. Future development of real-time spatial compound imaging will help address the bulk of general imaging applications by extending this technology to curved array transducers, tissue harmonics, panoramic imaging, and three-dimensional sonography.