ORIGINAL ARTICLES
Multiplane Transesophageal Echocardiography: Latest Evolution in an Imaging Revolution Jos R.T.C. Roelandt, MD, PhD, FACC, Ian R. Thomson, MD,' Wim B. Vletter, Pieter Brommersma, Nicolas Born, PhD, and David T. Linker, MD, Rotterdam) The Netherlands
Multiplane imaging with a rotating phased-array transducer from within the esophagus represents the latest development in transesophageal cardiac ultrasound. Transverse, longitudinal, and all possible intermediate oblique planes are easily obtained from the same transducer with minimal probe manipulation. Three-dimensional conceptualization of complex structures and pathologic conditions is facilitated. The major advantages are a simplified examination procedure and much less patient discomfort than monoplane and biplane probe imaging. (J AM Soc EcHOCARDIOGR 1992;5:361-7.)
Transesophageal echocardiography is a major ad-
vance in the noninvasive assessment of cardiac disease that has found wide application. The technique is useful for patients in whom transthoracic imaging is inadequate and, more important, it allows visualization of cardiac structures not seen from the precordium.1 However, with standard monoplane transducer, imaging of the heart and great vessels is restricted to the transverse plane. A biplane transducer system was developed in 1982 to obtain both transverse and longitudinal imaging planes. 2 Biplane transesophageal imaging partially overcomes the lack of versatility associated with transverse imaging and expands the diagnostic capabilities. 3 A rotating phased-array transducer was suggested by Souquer2 and Hanrath et al. 4 in 1982 and designed by Harui et al. 5 in 1985. With this multiplane system, views along an infinite number of imaging planes can be obtained. However, clinical experience with multiplane imaging is limited. 6 We constructed a multiplanar imaging system at the Thoraxcenter and now report our preliminary experience. From the Thoraxcenter, University Hospital Dijkzigt and Erasmus University. 'Dr. Ian R. Thomson was a senior research fellow at the Thoraxcenter from the Department of Anesthesiology, University of Manitoba, Winnipeg, Manitoba, Canada. Reprint requests: J. Roelandt, MD, Thoraxcentre, Bd 408, P.O. Box 1738, 3000 DR ROTTERDAM, The Netherlands. 27/l/37396
Figure 1 The multiplane (Varioplane) transesophageal probe (left) is shown together with a conventional5 MHz biplane transesophageal probe (right). The housing at the tip of the multi plane probe contains a 5 MHz, 64-element phased-array transducer that can be rotated through 180 degrees.
METHODS
The Multiplane Transducer (Varioplane)
The scanhead of the V arioplane transducer developed by P. Brommersma at the Thoraxcenter consists of 361
362
Roelandt et al.
Journal of the American Society of Echocardiography
Figure 2 Schema of the multiplane probe showing how transducer and imaging plane can be rotated from an intermediate transverse position (T) in opposite directions over 90 degrees to obtain longirudinal planes (L and L'). All intermediate oblique planes are sequentially visualized.
Figure 3 Schema of the heart in lefr lateral view with orthogonal planes showing the mirror two-chamber views by use of longirudinal planes (Land L') and short-axis view through the mitral valve orifice with the transverse plane (T). Transverse plane is the intermediate transducer position in the multiplane scanhead from which it can be rotated to positions L and L' . a.ML, Anterior mitral leaflet; LV, lefr ventricle; MVO, mitral valve orifice; pML, posterior mitral leaflet; R V, right ventricle.
a 5 MHz, 64-element phased-array that rotates in a special housing fitted to the end of a standard gastroscope (ACMI, Stamford, Conn.) (Figure 1). This configuration permits transverse, longitudinal, and
all intermediate planes to be visualized. To achieve maximum imaging capability, the transducer must rotate through 180 degrees. Transverse imaging is realized with the transducer in the midposition. Plus-
Volume 5 Number 4 July-August 1992
Multiplane transesophageal echocardiography 363
minus 90 degrees rotation from this intermediate position permits longitudinal imaging (Figures 2 to 4). The endoscope steering house has two control knobs. In the original gastroscope they are used for anteflexion and lateral flexion. The Varioplane system uses one control for anteroposterior flexion. Lateral flexion is eliminated and the second control is used to rotate the transducer within the housing at the probe tip. The need for lateral flexion is obviated by the rotational capability of the transducer. Phased-array transducers are customarily rectangular. The dimension of one side is dictated by the length of the elements and the other by the number of elements times their width. The latter is dictated by the operating frequency. A standard 5 MHz, 64element phased-array transducer is a rectangle of 9 x 10 mm. To accommodate such a transducer within the Varioplane housing, a probe tip of 17 mm is needed. Such dimensions are clearly impractical. However, a 5 MHz, 64-element, phased-array transducer can be accommodated within an acceptable tip size if a rectangular transducer is made octagonal by amputating the comers. Measurement of the acoustic beam profile of our octagonal array revealed no loss of main lobe sensitivity. Sidelobes actually decreased, thus improving image quality. The total width of the probe tip was reduced to 15 mm. The thickness is 11 mm and the length 40 mm. Out-of-plane focusing of the acoustic beam is achieved with an acoustic lens that covers the array. This lens also acts as a seal between the rotating parts and the solid housing. The current prototype has no electronic position feedback, so there is no indication of the position of the imaging plane on the monitor. However, during the examination, the operator uses the position of the control knob as an indication of the imaging planes. Patients Studied
Our initial experience reported here is based on 32 studies in 29 adult patients (20 men and 9 women, ages 22 years to 78 years). In two patients the transesophageal studies were performed in the operating room for assessment of the regurgitant mitral valve before and after repair. The clinical questions for referral to the outpatient department were as follows: assessment of native valve function in five patients, of which three were suspected ofhaving endocarditis; eight patients had a prosthetic valve, with suspected dysfunction in four and endocarditis in another four; four patients had a conduit (two in the ascending and two in the descending aorta); five were referred after embolic stroke for possible intracardiac source; seven patients were referred for evaluation of aortic pathology; and one patient had an atrial septal defect.
Figure 4 Transesophageal images corresponding to the schematics shown in Figure 3. A, In this orientation of the longitudinal plane, the two-chamber view is visualized with mitral valve to right and left ventricular apex to left. B, Short-axis view through mitral valve. C, Two-chamber view in longitudinal plane that is mirror-image of A. In this position of the longitudinal plane the mitral valve inflow is to the left and left ventricular apex to the right.
The procedure was fully explained and informed consent obtained. Precaution, preparation of the patients, and insertion of the V arioplane probe followed the standard procedures described in litera-
Journal of the American Society of Echocardiography
364 Roelandt et al.
Figure 5 A, Orifice of the aortic valve (A V) and morphology of the cusps are well delineated. The raphe of the fused cusps, as well as the calcifications, are clearly depicted. B, In this intermediate almost perpendicular plane to the short axis view, the valve morphology and the aneurysm of the ascending aorta (Ao Asc) are shown in great detail. LA, Left atrium; PA, pulmonary artery; RA, right atrium; R VOT, right ventricular outflow tract.
ture. 1 Positioning of the probe was guided by realtime two-dimensional imaging in the transverse plane. The examination was well tolerated in all patients and no difficulties were encountered with manipulation of the probe during the examination. RESULTS
A systematic acqulSltiOn of cardiac images started with the transducer at the level of the gastric fundus, then at the lower esophagus, followed by the upper esophagus. Transverse, longitudinal, and all possible intermediate planes were obtained from the same transducer location with minimal probe movement. Subtle rotational adjustments allowed optimization of the imaging plane for visualization of specific structures. In general, the multitude of imaging planes available prolonged the duration of the examination, but the procedure was well tolerated because of reduced transducer manipulation. Three patient studies are presented here to illustrate specific advantages of the V arioplane technique. Patient 1
A 57-year-old man, known to have mild aortic regurgitation, developed atypical chest pain. Chest X-ray film showed marked aneurysmal dilatation of the ascending aorta and he was referred to our echo laboratory for a transesophageal study. On auscultation, a grade II/VI systolic and a grade III/VI holodiastolic murmur were heard along the left parasternal border. Multiplane examination allowed de-
tailed visualization of a bicuspid aortic valve in intermediate imaging planes (Figure 5). It was very difficult to obtain a short-axis view of the aortic valve with all these details in either the transverse or longitudinal imaging planes because of the position of the valve. Patient2
This 25-year-old man was referred for valve surgery because of severe aortic and mitral regurgitation after treated endocarditis. Precordial echocardiography showed a vegetation on the right aortic valve cusp prolapsing into the outflow tract. An abnormality of the mitral valve that was believed to be chordal rupture was present. A transesophageal multi planestudy was performed to analyze the mitral valve in more detail (Figure 6). A dissection of the anterior mitral valve leaflet and multiple perforations were found that were subsequently confirmed at surgery. Patient 3
This 42-year-old woman was transferred for aortic valve replacement because of congestive heart failure and aortic insufficiency caused by Staphylococcus aureus endocarditis. She also had immune complex glomerulonephritis. At surgery her valve was replaced with an aortic homograft. A perivalvular abscess cavity was cleaned out and obliterated by suturing. One week after surgery an echo-free space was found on precordial echo, anterior to the left ventricular outflow tract high in the interventricular septum. A transesophageal multiplane study was performed to delineate the extension of this space (Figure 7).
Volume 5 Number 4 July-August 1992
Multiplane transesophageal echocardiography 365
Figure 6 In (A) it is possible to see that there is a perforation and dissection of the anterior mitral valve leaflet with a semicircular membrane dissected from the atrial side of the leaftlet. There is a vegetation (Vt;g) on the aortic valve. In (B) it is possible to see the complex nature of this dissection, when the transducer is rotated slightly into a different plane. C shows the disturbed flow caused by massive central mitral insufficiency. Slight rotation of the transducer illustrates, (in D), that there are two additional jets of mitral regurgitation, possibly perforations of the anterior mitral leaflet (arrows). This was confirmed by surgery. Ao, Aorta; LA, left atrium; LV, left ventricle.
DISCUSSION
The lack of orthogonal planes with the standard monoplane systems limits visualization of longitudinally aligned structures. Three-dimensional conceptualization of the heart and complex structures such as the mitral valve apparatus is difficult and sometimes impossible. This difficulty is partially overcome with biplane imaging systems because orthogonal planes with sagitally aligned structures are now visualized. However, biplane systems have two separate transducers, necessitating repositioning of one transducer to optimize and to visualize the heart at exactly the same level. Relationships and three-dimensional conceptualization of complex structures may remain puzzling. A biplane phasedarray matrix transducer has been developed to over-
come this problem and allows biplane scanning from a single transducer position? However, this technology is complex and image quality remains less than optimal. Clearly,the impetus to develop a multiplane transducer was to overcome the limitations of monoplane and biplane transesophageal imaging systems, which are listed in Table l. The advantages of multiplane imaging are described in Table 2. The ease and success with which all transitional (oblique) planes are obtained from a single transducer position is the major advantage of multiplane over biplane imaging and undoubtedly increases the diagnostic yield. With minor rotational movements of the probe, the optimal plane is realized, providing detailed high-quality images of structures that do not lie close to the transverse or longitudinal planes. Left and right ventricular outflow tracts and conduits are
366
Journal of the American Society of Echocardiography
Roelandt et al.
Figure 7 In (A) it is possible to see an echo-free space in the superior portion of the septum (marked with a star). Rotating the transducer in B shows that this space extends to the ascending aorta. C shows that there is also a posterior extension of this echo-free space, and with rotation of the transducer it is demonstrated to be quite large in D. Ao, Aorta; A V, aortic valve; LA, left atrium; LV, left ventricle; RA, right atrium; R V, right ventricle.
Table 1
Limitations of monoplane and biplane transesophageal echocardiography
Monoplane Single plane limits appreciation of three-dimensional relationships Certain cross-sections are difficult to visualize Excessive probe manipulation Biplane Limited to two fixed (orthogonal) imaging planes Some oblique planes are not visualized or require excessive lateral flexion The transducers are at different levels Proximal transducer may not have adequate contact, requiring repositioning
Table 2
Advantages of multi plane transesophageal echocardiography
Transitional (oblique) planes reduce interpretation problems associated with both single and biplane TEE Best for three-dimensional conceptualization and computer reconstruction Minimal repositioning is required. This facilitates the examination procedure with less discomfort to the patient Ideal for visualization of complex structures Optimization of imaging and Doppler flow mapping
obvious examples, and long-axis views of these structures are now readily obtainable. Duration of the examination was prolonged in this early experience because of the lack of familarity with the oblique views. We expect this difference to dis-
appear with further experience, and that examination with a Varioplane probe will probably be of shorter duration than with a single-plane probe because of greater ease of imaging longitudinal and oblique structures.
Volume 5 Number4 July-August 1992
Multiplane imaging is ideal for visualizing connections between structures that do not lie in either the transversal or longitudinal planes, inasmuch as no repositioning or switching to another transducer is necessary. Thus, off-axis spatial relationships are now available. From our limited experience it is evident that complex, spatially oriented structures, such as the mitral valve and coronary arteries, are more easily and completely assessed with multiplane than with monoplane and biplane systems. For example, the closure line of the mitral valve is now readily and completely visualized from its anterolateral to its posteromedial commissure. Both coaptation and apposition of the leaflets can be assessed. This information can be crucial to the surgeon who attempts mitral valve repair. The objective evaluation of the independent additional information that can be obtained with the multiplane system in comparison with the biplane systems is a difficult problem, inasmuch as it involves both practical and ethical aspects. Such a study would require the sequential introduction of a multiplane and biplane probe in the same patient by two independent investigators with similar skills and expenence. Our prototype system has no electronic feedback on the video screen to indicate the transducer position relative to the standard orthogonal planes. Such a facility may have advantages when reading images off-line from video recordings. This situation is similar, however, to transthoracic cross-sectional studies where a multitude of intermediate imaging planes is
Multiplane transesophageal echocardiography 367
available. It seems that there is no compelling need for such a position indicator unless three-dimensional reconstruction is considered. This latter development is an important future application of the V arioplane technique.
REFERENCES l. Mitchell MM, Sutherland GR, Gussenhoven EJ, Taams MA,
2.
3.
4.
5. 6.
7.
Roelandt J. Transesophageal echocardiography. J AM Soc ECHOCARDIOGR 1988;1:362-77. Souquet J. Phased array transducer technology for transesophageal imaging of the heart: current status and future aspects. In: Hanrath et al., eds. Cardiovascular diagnosis by ultrasound. The Hague: Martinus Nijhoff, 1982:251-9. Seward JB, Khandheria BK, Edwards WD, Oh JK, Freeman WK, Tajik AJ. Biplanar transesophageal echocardiography: anatomic correlations, image orientation, and clinical application. Mayo Clin Proc 1990;65:1193-213. Hanrath P, Schluter H, Langenstein BA, Polster J, Engel S. Transesophageal horizontal and sagittal imaging of the heart with a phased array system. Initial clinical results. In: Hanrath et al., eds. Cardiovascular diagnosis by ultrasound. The Hague: Martinus Nijhoff, 1982:251-9. Harui N, Souquet J. Transesophageal echocardiography scanhead. United States Patent No 4.543.960, October 1, 1985. FlachskampfFA, Hoffmann R, Hanrath P. Experience with a transesophageal echo-transducer allowing full rotation of the viewing plane: the omniplane probe [Abstract]. J Am Coli Cardiol1991;17(suppl A):34A. Omoto R, Kyo S, Matsumura M, Adachi H, Maruyama M, Matsunaka T. New direction of biplane rransesophageal echocardiography with special emphasis on real-time biplane imaging and matrix phased-array biplane transducer. Echocardiography 1990;7:691-8.
Multiplane Transesophageal Echocardiography: Latest Evolution in an Imaging Revolution Jos R.T.C. Roelandt, MD, PhD, FACC, Ian R. Thomson, MD,' Wim B. Vletter, Pieter Brommersma, Nicolas Born, PhD, and David T. Linker, MD, Rotterdam) The Netherlands
Multiplane imaging with a rotating phased-array transducer from within the esophagus represents the latest development in transesophageal cardiac ultrasound. Transverse, longitudinal, and all possible intermediate oblique planes are easily obtained from the same transducer with minimal probe manipulation. Three-dimensional conceptualization of complex structures and pathologic conditions is facilitated. The major advantages are a simplified examination procedure and much less patient discomfort than monoplane and biplane probe imaging. (J AM Soc EcHOCARDIOGR 1992;5:361-7.)
Transesophageal echocardiography is a major ad-
vance in the noninvasive assessment of cardiac disease that has found wide application. The technique is useful for patients in whom transthoracic imaging is inadequate and, more important, it allows visualization of cardiac structures not seen from the precordium.1 However, with standard monoplane transducer, imaging of the heart and great vessels is restricted to the transverse plane. A biplane transducer system was developed in 1982 to obtain both transverse and longitudinal imaging planes. 2 Biplane transesophageal imaging partially overcomes the lack of versatility associated with transverse imaging and expands the diagnostic capabilities. 3 A rotating phased-array transducer was suggested by Souquer2 and Hanrath et al. 4 in 1982 and designed by Harui et al. 5 in 1985. With this multiplane system, views along an infinite number of imaging planes can be obtained. However, clinical experience with multiplane imaging is limited. 6 We constructed a multiplanar imaging system at the Thoraxcenter and now report our preliminary experience. From the Thoraxcenter, University Hospital Dijkzigt and Erasmus University. 'Dr. Ian R. Thomson was a senior research fellow at the Thoraxcenter from the Department of Anesthesiology, University of Manitoba, Winnipeg, Manitoba, Canada. Reprint requests: J. Roelandt, MD, Thoraxcentre, Bd 408, P.O. Box 1738, 3000 DR ROTTERDAM, The Netherlands. 27/l/37396
Figure 1 The multiplane (Varioplane) transesophageal probe (left) is shown together with a conventional5 MHz biplane transesophageal probe (right). The housing at the tip of the multi plane probe contains a 5 MHz, 64-element phased-array transducer that can be rotated through 180 degrees.
METHODS
The Multiplane Transducer (Varioplane)
The scanhead of the V arioplane transducer developed by P. Brommersma at the Thoraxcenter consists of 361
362
Roelandt et al.
Journal of the American Society of Echocardiography
Figure 2 Schema of the multiplane probe showing how transducer and imaging plane can be rotated from an intermediate transverse position (T) in opposite directions over 90 degrees to obtain longirudinal planes (L and L'). All intermediate oblique planes are sequentially visualized.
Figure 3 Schema of the heart in lefr lateral view with orthogonal planes showing the mirror two-chamber views by use of longirudinal planes (Land L') and short-axis view through the mitral valve orifice with the transverse plane (T). Transverse plane is the intermediate transducer position in the multiplane scanhead from which it can be rotated to positions L and L' . a.ML, Anterior mitral leaflet; LV, lefr ventricle; MVO, mitral valve orifice; pML, posterior mitral leaflet; R V, right ventricle.
a 5 MHz, 64-element phased-array that rotates in a special housing fitted to the end of a standard gastroscope (ACMI, Stamford, Conn.) (Figure 1). This configuration permits transverse, longitudinal, and
all intermediate planes to be visualized. To achieve maximum imaging capability, the transducer must rotate through 180 degrees. Transverse imaging is realized with the transducer in the midposition. Plus-
Volume 5 Number 4 July-August 1992
Multiplane transesophageal echocardiography 363
minus 90 degrees rotation from this intermediate position permits longitudinal imaging (Figures 2 to 4). The endoscope steering house has two control knobs. In the original gastroscope they are used for anteflexion and lateral flexion. The Varioplane system uses one control for anteroposterior flexion. Lateral flexion is eliminated and the second control is used to rotate the transducer within the housing at the probe tip. The need for lateral flexion is obviated by the rotational capability of the transducer. Phased-array transducers are customarily rectangular. The dimension of one side is dictated by the length of the elements and the other by the number of elements times their width. The latter is dictated by the operating frequency. A standard 5 MHz, 64element phased-array transducer is a rectangle of 9 x 10 mm. To accommodate such a transducer within the Varioplane housing, a probe tip of 17 mm is needed. Such dimensions are clearly impractical. However, a 5 MHz, 64-element, phased-array transducer can be accommodated within an acceptable tip size if a rectangular transducer is made octagonal by amputating the comers. Measurement of the acoustic beam profile of our octagonal array revealed no loss of main lobe sensitivity. Sidelobes actually decreased, thus improving image quality. The total width of the probe tip was reduced to 15 mm. The thickness is 11 mm and the length 40 mm. Out-of-plane focusing of the acoustic beam is achieved with an acoustic lens that covers the array. This lens also acts as a seal between the rotating parts and the solid housing. The current prototype has no electronic position feedback, so there is no indication of the position of the imaging plane on the monitor. However, during the examination, the operator uses the position of the control knob as an indication of the imaging planes. Patients Studied
Our initial experience reported here is based on 32 studies in 29 adult patients (20 men and 9 women, ages 22 years to 78 years). In two patients the transesophageal studies were performed in the operating room for assessment of the regurgitant mitral valve before and after repair. The clinical questions for referral to the outpatient department were as follows: assessment of native valve function in five patients, of which three were suspected ofhaving endocarditis; eight patients had a prosthetic valve, with suspected dysfunction in four and endocarditis in another four; four patients had a conduit (two in the ascending and two in the descending aorta); five were referred after embolic stroke for possible intracardiac source; seven patients were referred for evaluation of aortic pathology; and one patient had an atrial septal defect.
Figure 4 Transesophageal images corresponding to the schematics shown in Figure 3. A, In this orientation of the longitudinal plane, the two-chamber view is visualized with mitral valve to right and left ventricular apex to left. B, Short-axis view through mitral valve. C, Two-chamber view in longitudinal plane that is mirror-image of A. In this position of the longitudinal plane the mitral valve inflow is to the left and left ventricular apex to the right.
The procedure was fully explained and informed consent obtained. Precaution, preparation of the patients, and insertion of the V arioplane probe followed the standard procedures described in litera-
Journal of the American Society of Echocardiography
364 Roelandt et al.
Figure 5 A, Orifice of the aortic valve (A V) and morphology of the cusps are well delineated. The raphe of the fused cusps, as well as the calcifications, are clearly depicted. B, In this intermediate almost perpendicular plane to the short axis view, the valve morphology and the aneurysm of the ascending aorta (Ao Asc) are shown in great detail. LA, Left atrium; PA, pulmonary artery; RA, right atrium; R VOT, right ventricular outflow tract.
ture. 1 Positioning of the probe was guided by realtime two-dimensional imaging in the transverse plane. The examination was well tolerated in all patients and no difficulties were encountered with manipulation of the probe during the examination. RESULTS
A systematic acqulSltiOn of cardiac images started with the transducer at the level of the gastric fundus, then at the lower esophagus, followed by the upper esophagus. Transverse, longitudinal, and all possible intermediate planes were obtained from the same transducer location with minimal probe movement. Subtle rotational adjustments allowed optimization of the imaging plane for visualization of specific structures. In general, the multitude of imaging planes available prolonged the duration of the examination, but the procedure was well tolerated because of reduced transducer manipulation. Three patient studies are presented here to illustrate specific advantages of the V arioplane technique. Patient 1
A 57-year-old man, known to have mild aortic regurgitation, developed atypical chest pain. Chest X-ray film showed marked aneurysmal dilatation of the ascending aorta and he was referred to our echo laboratory for a transesophageal study. On auscultation, a grade II/VI systolic and a grade III/VI holodiastolic murmur were heard along the left parasternal border. Multiplane examination allowed de-
tailed visualization of a bicuspid aortic valve in intermediate imaging planes (Figure 5). It was very difficult to obtain a short-axis view of the aortic valve with all these details in either the transverse or longitudinal imaging planes because of the position of the valve. Patient2
This 25-year-old man was referred for valve surgery because of severe aortic and mitral regurgitation after treated endocarditis. Precordial echocardiography showed a vegetation on the right aortic valve cusp prolapsing into the outflow tract. An abnormality of the mitral valve that was believed to be chordal rupture was present. A transesophageal multi planestudy was performed to analyze the mitral valve in more detail (Figure 6). A dissection of the anterior mitral valve leaflet and multiple perforations were found that were subsequently confirmed at surgery. Patient 3
This 42-year-old woman was transferred for aortic valve replacement because of congestive heart failure and aortic insufficiency caused by Staphylococcus aureus endocarditis. She also had immune complex glomerulonephritis. At surgery her valve was replaced with an aortic homograft. A perivalvular abscess cavity was cleaned out and obliterated by suturing. One week after surgery an echo-free space was found on precordial echo, anterior to the left ventricular outflow tract high in the interventricular septum. A transesophageal multiplane study was performed to delineate the extension of this space (Figure 7).
Volume 5 Number 4 July-August 1992
Multiplane transesophageal echocardiography 365
Figure 6 In (A) it is possible to see that there is a perforation and dissection of the anterior mitral valve leaflet with a semicircular membrane dissected from the atrial side of the leaftlet. There is a vegetation (Vt;g) on the aortic valve. In (B) it is possible to see the complex nature of this dissection, when the transducer is rotated slightly into a different plane. C shows the disturbed flow caused by massive central mitral insufficiency. Slight rotation of the transducer illustrates, (in D), that there are two additional jets of mitral regurgitation, possibly perforations of the anterior mitral leaflet (arrows). This was confirmed by surgery. Ao, Aorta; LA, left atrium; LV, left ventricle.
DISCUSSION
The lack of orthogonal planes with the standard monoplane systems limits visualization of longitudinally aligned structures. Three-dimensional conceptualization of the heart and complex structures such as the mitral valve apparatus is difficult and sometimes impossible. This difficulty is partially overcome with biplane imaging systems because orthogonal planes with sagitally aligned structures are now visualized. However, biplane systems have two separate transducers, necessitating repositioning of one transducer to optimize and to visualize the heart at exactly the same level. Relationships and three-dimensional conceptualization of complex structures may remain puzzling. A biplane phasedarray matrix transducer has been developed to over-
come this problem and allows biplane scanning from a single transducer position? However, this technology is complex and image quality remains less than optimal. Clearly,the impetus to develop a multiplane transducer was to overcome the limitations of monoplane and biplane transesophageal imaging systems, which are listed in Table l. The advantages of multiplane imaging are described in Table 2. The ease and success with which all transitional (oblique) planes are obtained from a single transducer position is the major advantage of multiplane over biplane imaging and undoubtedly increases the diagnostic yield. With minor rotational movements of the probe, the optimal plane is realized, providing detailed high-quality images of structures that do not lie close to the transverse or longitudinal planes. Left and right ventricular outflow tracts and conduits are
366
Journal of the American Society of Echocardiography
Roelandt et al.
Figure 7 In (A) it is possible to see an echo-free space in the superior portion of the septum (marked with a star). Rotating the transducer in B shows that this space extends to the ascending aorta. C shows that there is also a posterior extension of this echo-free space, and with rotation of the transducer it is demonstrated to be quite large in D. Ao, Aorta; A V, aortic valve; LA, left atrium; LV, left ventricle; RA, right atrium; R V, right ventricle.
Table 1
Limitations of monoplane and biplane transesophageal echocardiography
Monoplane Single plane limits appreciation of three-dimensional relationships Certain cross-sections are difficult to visualize Excessive probe manipulation Biplane Limited to two fixed (orthogonal) imaging planes Some oblique planes are not visualized or require excessive lateral flexion The transducers are at different levels Proximal transducer may not have adequate contact, requiring repositioning
Table 2
Advantages of multi plane transesophageal echocardiography
Transitional (oblique) planes reduce interpretation problems associated with both single and biplane TEE Best for three-dimensional conceptualization and computer reconstruction Minimal repositioning is required. This facilitates the examination procedure with less discomfort to the patient Ideal for visualization of complex structures Optimization of imaging and Doppler flow mapping
obvious examples, and long-axis views of these structures are now readily obtainable. Duration of the examination was prolonged in this early experience because of the lack of familarity with the oblique views. We expect this difference to dis-
appear with further experience, and that examination with a Varioplane probe will probably be of shorter duration than with a single-plane probe because of greater ease of imaging longitudinal and oblique structures.
Volume 5 Number4 July-August 1992
Multiplane imaging is ideal for visualizing connections between structures that do not lie in either the transversal or longitudinal planes, inasmuch as no repositioning or switching to another transducer is necessary. Thus, off-axis spatial relationships are now available. From our limited experience it is evident that complex, spatially oriented structures, such as the mitral valve and coronary arteries, are more easily and completely assessed with multiplane than with monoplane and biplane systems. For example, the closure line of the mitral valve is now readily and completely visualized from its anterolateral to its posteromedial commissure. Both coaptation and apposition of the leaflets can be assessed. This information can be crucial to the surgeon who attempts mitral valve repair. The objective evaluation of the independent additional information that can be obtained with the multiplane system in comparison with the biplane systems is a difficult problem, inasmuch as it involves both practical and ethical aspects. Such a study would require the sequential introduction of a multiplane and biplane probe in the same patient by two independent investigators with similar skills and expenence. Our prototype system has no electronic feedback on the video screen to indicate the transducer position relative to the standard orthogonal planes. Such a facility may have advantages when reading images off-line from video recordings. This situation is similar, however, to transthoracic cross-sectional studies where a multitude of intermediate imaging planes is
Multiplane transesophageal echocardiography 367
available. It seems that there is no compelling need for such a position indicator unless three-dimensional reconstruction is considered. This latter development is an important future application of the V arioplane technique.
REFERENCES l. Mitchell MM, Sutherland GR, Gussenhoven EJ, Taams MA,
2.
3.
4.
5. 6.
7.
Roelandt J. Transesophageal echocardiography. J AM Soc ECHOCARDIOGR 1988;1:362-77. Souquet J. Phased array transducer technology for transesophageal imaging of the heart: current status and future aspects. In: Hanrath et al., eds. Cardiovascular diagnosis by ultrasound. The Hague: Martinus Nijhoff, 1982:251-9. Seward JB, Khandheria BK, Edwards WD, Oh JK, Freeman WK, Tajik AJ. Biplanar transesophageal echocardiography: anatomic correlations, image orientation, and clinical application. Mayo Clin Proc 1990;65:1193-213. Hanrath P, Schluter H, Langenstein BA, Polster J, Engel S. Transesophageal horizontal and sagittal imaging of the heart with a phased array system. Initial clinical results. In: Hanrath et al., eds. Cardiovascular diagnosis by ultrasound. The Hague: Martinus Nijhoff, 1982:251-9. Harui N, Souquet J. Transesophageal echocardiography scanhead. United States Patent No 4.543.960, October 1, 1985. FlachskampfFA, Hoffmann R, Hanrath P. Experience with a transesophageal echo-transducer allowing full rotation of the viewing plane: the omniplane probe [Abstract]. J Am Coli Cardiol1991;17(suppl A):34A. Omoto R, Kyo S, Matsumura M, Adachi H, Maruyama M, Matsunaka T. New direction of biplane rransesophageal echocardiography with special emphasis on real-time biplane imaging and matrix phased-array biplane transducer. Echocardiography 1990;7:691-8.
