© 2003 by European Society of Cardiology
Copyright © 2003, The European Society of Cardiology
The 50th anniversary of echocardiography: are we at the dawn of a new era?
Department of Cardiology, Thoraxcentre, Erasmus MC, Rotterdam, The Netherlands
Disease is very old, and nothing about it has changed.It is we who change, and we learn to recognise what was formally imperceptible.
J.M. Charcot (1825–1893)
Before the development of cardiovascular imaging techniques, clinicians could only imagine how the heart of their patients was contracting. It was not until the introduction of contrast ventriculography and quantitative methods for analysis in the early 1960s that objective data could be substituted for the subjective bedside observations. These developments irrevocably changed cardiology from an art to a science. Computer-aided systems were subsequently developed for more accurate analysis and reproducible measurements.
In the past 20 years, advances in digital techniques and the imagination and creativity of many have resulted in an enormous progress in complex cardiac imaging modalities including ultrasound imaging, SPECT, multislice-CT, MR and PET[1]. These advances will undoubtedly accelerate as our reliance on imaging techniques for management of cardiovascular disease will continue to increase[1].
Who could have predicted 30 years ago the impressive evolution of cardiac ultrasound imaging systems? The technique paralleled the developments in microprocessor technology, it did not mimic the existing imaging modalities by providing tomographic images of the heart and it introduced new pathophysiologic and diagnostic concepts. As a consequence, it opened new horizons for clinical research and made unique contributions to our understanding of cardiac disease. With the increasing imaging performance, the number of functions and Doppler assessment of hemodynamics, all of which can be applied in a wide variety of clinical scenarios, it has become the most widely disseminated cardiac imaging technology. Currently, more than one out of every four medical imaging studies is performed worldwide with ultrasound and the proportion is still increasing.
With the progress in miniaturisation and microprocessor technology cardiac ultrasound imaging continues to evolve rapidly (Fig. 1). We have now at one end the high-end full featured systems which integrate many modalities and functions and which are used both invasively and non-invasively (Table 1). However, all these functions and the augmented diagnostic capabilities have not only increased the complexity but have substantially increased the cost of these systems and the echocardiographic examination. Also, several functions in these high-end systems are only used for testing patho-physiological concepts and clinical research. Therefore, it seems logical to develop portable special dedicated systems with established functions for specific clinical applications. At the other end of the spectrum, small hand-carried systems with less functions but good imaging quality have been developed which are relatively inexpensive and can be used at the point-of-care as part of the physical examination.
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High-end ultrasound imaging systems |
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 Top High-end ultrasound imaging... Special dedicated ultrasound...Hand-held ultrasound systemsConclusionReferences |
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Currently available high-end ultrasound systems allow an integrated assessment of cardiac function and hemodynamics with an unprecedented versatility. The echocardiography laboratory can therefore appropriately be called ‘the non-invasive imaging and hemodynamic laboratory’. The impact on our diagnostic capabilities has been enormous and the practice of cardiology has been changed permanently. In day-to-day cardiological practice, ultrasound imaging and Doppler assessment are now the first cardiac examination whenever cardiac disease is suspected and a definitive diagnosis is often made at a relatively low cost when compared to cardiac catheterisation and angiography which often can be avoided.
However, the integration of the many functions in the high-end ultrasound systems makes them very complex, although their operation becomes simpler to image and to optimise the image quality. It should be realised, however, that some functions are only used in tertiary referral centres or in clinical research. The competition between manufacturers has been largely responsible for the incorporation of these functions even before their impact on patient management and outcome was validated. Randomised clinical trials should have an important role in the evaluation of diagnostic imaging methods in the future.
The latest development in cardiac ultrasound is real-time volumetric imaging which will replace three-dimensional reconstruction from gated two-dimensional image acquisition[2]. In both systems a volumetric dataset is created which can be rotated and rapidly sliced to show (gross) cardiac anatomy from different viewpoints. In comparison with two-dimensional imaging, three-dimensional imaging more faithfully replicates the complex cardiac morphology and its contents. Quantitative methods allow to exploit the spatial information which is inherently present in the volumetric presentation for more accurate measurements of surfaces, orifices, volumes and shapes than with two-dimensional echocardiography. However, the time resolution of real-time three-dimensional imaging is (very) limited. There is a lot of detailed diagnostic information available from analysing motion patterns and time intervals from M-mode echocardiography. These capabilities together with Doppler flow velocity recordings will always remain the mainstay for a complete assessment of a cardiac disorder.
In the future, three-dimensional imaging in combination with computer-assisted data manipulation and display will allow exciting data presentations of otherwise nonvisible dynamic cardiac phenomena such as elastography, strain rate, electrical activation, etc. With further developments in microprocessor technology, the number of visualised dynamic cardiac (patho)-physiologic phenomena and biochemistry as opposed to structure and their imaging solutions appears infinite. Mathematical modeling is becoming a new paradigm in cardiac imaging[3]. The imagination of researchers and new visual displays of these phenomena with modern computer graphics will undoubtedly help to further elucidate and better understand the complex functions of the heart.
Another important medical frontier opened by three-dimensional echocardiography is virtual reality, the immersive environment which is created by a computer combining three-dimensional datasets of a patient with, e.g., all the information that you know about the normal heart and its pathology or from, e.g., the ‘visible human’[4]. Virtual reality allows the physician to interact with these data and heralds a revolution for medical training, internet-based distance learning, on-line research between centres via ultra-high speed networks all over the world[5], diagnosis and treatment by e.g. remote robot interventions, etc.
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Special dedicated ultrasound systems |
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TopHigh-end ultrasound imaging...Special dedicated ultrasound...Hand-held ultrasound systemsConclusionReferences |
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There are many cardiac conditions and clinical scenarios in which the clinical question to be answered is limited. In these clinical scenarios only a limited number of functions with little examination protocols are needed (e.g. follow-up of most patients often requires only to measure left ventricular function and is the most common referral question in most laboratories). Currently, more appropriate mobile and portable systems with limited functions and good imaging performance for the clinic and office practice are becoming available. Their development should be further stimulated.
For example, fast continuous rotational scanning can be performed with a newly developed transducer system using a standard phased-array transducer and ultrasound system which allows the acquisition of 16 volumetric datasets/s[6]. Automatic analysis of the LV endocardial contour allows rapid calculation of LV volumes, ejection fraction and quantitative wall motion analysis. Such a special dedicated instrument may offer advantages for follow-up studies of LV function, stress echocardiography and interventional procedures (e.g. synchronisation therapy in heart failure).
Intraoperative examination of the aorta and post-repair testing of an intracardiac defect of a mitral valve or the rapid screening for a major cardiac problem in the emergency and intensive care room require limited modalities and functions. In these situations a portable system with good imaging performance and colour flow imaging allows to answer most of the questions or a rapid orientation for targetted referral.
Guiding interventions in the electrophysiology laboratory (placing catheters) and monitoring device closure in the interventional laboratory can be achieved with portable systems equipped with intracardiac imaging catheters. These systems are currently available and increasingly used.
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Hand-held ultrasound systems |
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TopHigh-end ultrasound imaging...Special dedicated ultrasound...Hand-held ultrasound systemsConclusionReferences |
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The "Stethoscope" of the 3rd Millennium
Microcomputer technology has led to the construction of small and powerful portable and hand-held ultrasound systems[7]. This is a logical development. Indeed, the history of medical devices indicates that there is always a trend to miniaturisation and suggests that the ‘high-end’ systems will become smaller and smaller in the future (Fig. 2).
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The smallest currently available system is almost pocket size and have excellent imaging performance that rivals that of standard equipment. Recent systems have also limited but essential Doppler functions and allow a comprehensive echo/Doppler examination. They can be used as part of the physical examination at the point-of-care anytime, anywhere in new healthcare settings — office practice, remote and difficult accessible areas, war zones, space travel, etc. Traditionally, our physical cardiac examination has been dependent on inspection, palpation and auscultation. Its shortcomings for the diagnosis of common cardiac disorders are well documented and these devices have the potential to complete our physical senses by directly seeing the ‘invisible heart and its pathology’ inside the chest (ultrasound stethoscopy). They will not replace the physical examination but considerably augment its yield and accuracy at the first contact with the patient (Table 2)[8]. It is also recognised that unsuspected and not clinically apparent cardiac abnormalities are regularly detected by a simple and limited echo/Doppler examination (LV dysfunction, hypertrophy, valve abnormalities, pericardial diseases, mass lesions). Who can argue against getting more information at the point of care?
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The advantages of these small devices are their direct availability, their use with greater flexibility and the shorter time to perform a study than with standard equipment in a variety of clinical scenarios.
I believe that these systems should be developed towards smaller, simple to use and cheaper to allow accurate detection of common cardiac abnormalities for specific screening programs. Whenever an abnormality is found, these patients must be referred for complete assessment. However, physicians will have to learn how to use these devices and how to interpret the images to detect basic cardiac conditions, abnormalities and not to make a definitive diagnosis. The level of competence required may differ depending on the application and clinical environment under consideration e.g. rapid screening and diagnosing acute problems in an emergency environment is different from answering referral questions in the outpatient clinic or identifying cardiac abnormalities in office practice. Properly managed, this shift in practice will greatly benefit the patients. The satisfaction and the value of the physical examination so often neglected in our technological age may be rediscovered by the younger generation of cardiologists by the insights gained from using ultrasound stethoscopy and lead to a renaissance of the physical examination in the third millennium.
Spectacular developments may further be expected from further miniaturisation of imaging techniques and biophysical sensors leading to robotic microsystems for diagnosis. Why not consider an implantable device that monitors left ventricular dimensions similar to sonocardiometry[9] in patients with heart failure and expensive cardiac support devices? Using such robots to sail like submarines through the human blood vessels to make local images, to do investigations and take therapeutic actions seems pure fantasy now. Such ‘micromachines’ may become a reality before the end of this century.
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Conclusion |
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TopHigh-end ultrasound imaging...Special dedicated ultrasound...Hand-held ultrasound systemsConclusionReferences |
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The major challenge of clinicians is to understand the characteristics of new ultrasound imaging modalities, to integrate them in an intelligent and cost-effective way into the clinical decision-making process and to extract from them the maximum objective information. Bias or subjectivity can be introduced into image interpretation through our emotional awareness of a patient's condition and can diminish the value of any imaging system. Therefore, computer-aided analysis and quantitative data extraction is mandatory. Because of the sophistication of the systems, the increasing number of indications and complex clinical questions the need for specific training programs and certification will grow. Indeed, the real value of any imaging technology is intimately dependent on our knowledge and our intellectual contributions: how, when and in what clinical scenario will a system have its optimal clinical impact. It is difficult to imagine what the impact of advanced analytic software, microsystems and multi-dimensional imaging will be on the use of ultrasound imaging and the practice of cardiology in the future. Without any doubt, we are at the dawn of a new era and revolutionary changes are ahead — use your imagination!
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References |
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TopHigh-end ultrasound imaging...Special dedicated ultrasound...Hand-held ultrasound systemsConclusionReferences |
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- Roelandt J.R.T.C. Seeing the invisible: a short history of cardiac imaging. Eur J Echocardiogr (2000) 1:8–11.
[Free Full Text] - Roelandt J.R.T.C. Three-dimensional echocardiography: the future today! Comput Graph (2000) 24:715–729.[CrossRef]
- Seward J.B., Belohlavek M., Kinter T.M., Greenleaf J.F. Evolving era of multidimensional medical imaging. Mayo Clin Proc (1999) 74:399–414.[ISI][Medline]
- Bruining N., Lancee C.T., Roelandt J.R.T.C., Bom N. Three-dimensional echocardiography paves the way towards virtual reality. Ultrasound Med Biol (2000) 7:1065–1074.
- Bruining N., Hendriks B., Boelhouwer L., et al. Tele-echocardiography at the Thoraxcentre. Thoraxcentre J (2002) 14/4:84–87.
- Djoa K.K., de Jong N., van Egmond F.C., et al. A fast rotating scanning unit for real-time three-dimensional echo data acquisition. Ultrasound Med Biol (2000) 26:863–869.[CrossRef][ISI][Medline]
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[Free Full Text] - Vourvouri E.C., Koroleva L.Y., ten Cate F.J., et al. Clinical utility and cost effectiveness of a personal ultrasound imager for cardiac evaluation during consultation rounds in patients with suspected cardiac disease. Heart (2003) 89:727–730.
[Abstract/Free Full Text] - Rushmer R.F., Franklin D.L., Ellis R.M. Left ventricular dimensions recorded by sonocardiometry. Circ Res (1956) 4:684–688.
[Abstract/Free Full Text]
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  T. Buck and R. Erbel Should contrast be routinely used for echocardiographic assessment of left ventricular function? A matter of appropriateness Eur. Heart J., March 2, 2005; 26(6): 534 - 535. [Full Text] [PDF]
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