How to use Tissue Doppler and Strain Imaging in Clinical daily practice Abdulhalim J Kinsara Ass professor Head of cardiology King Saud Bin Abdulaziz university, COM King Abdulaziz medical city, king faisal cardiac center 1
why New imaging technologies provide a unique window into myocardial mechanics helping to better understand the pathophysiologic mechanisms of cardiovascular disease
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Myocardial Strain • Strain – deformation of myocardial fibers produced by applying a mechanical or electrical force , measured in % change • Deformation a change in lengthening or shortening in relation to original length – Negative strain myocardial fibers shorten or compress in relation to original length – Positive Strain myocardial fibers lengthen or stretch in relation to original length 3
Strain is a dimensionless index of change in length Strain ( % ) = (L - L0)/ L0 L L0
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• For 2-D or 3-D deformations, the concept of strain becomes more complex since shear strains add changes that might not occur in any of the coordinate directions. Therefore, new approaches have been developed in order to assess the 2D motion and deformation based on speckle tracking.
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• this speckle pattern characterises the underlying myocardial tissue acoustically and is assumed to be unique for each myocardial segment-serve as a fingerprint of the myocardial segment. •
Tracking of the acoustic pattern during the cardiac cycle allows to follow the motion and the deformation of this myocardial segment.
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Complex Motion of Myocardial Fibers
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Three Main Types of Strain • Longitudinal strain – systolic myocardial shortening from base to apex (negative strain) • Track subendocardial fibers • More longitudinal strain at base than apex
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Longitudinal Strain
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Three Main Types of Strain • Circumferential strain – reflecting intramural circumferential shortening (negative strain) • Most stable – mid wall • Short axis Septum and posterior highest
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Circumferential Strain
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Three Main Types of Strain • Radial strain – %thickening of the heart muscle toward the center from the endocardium to epicardium (transmural) positive strain • Can identify dyssynchrony • Least stable curve • Compare to average thickening values by MRI • Short axis view 12
Transverse / Radial Strain
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Transverse
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Transverse / Radial Strain
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Strain Calculation • End – diastole (LV short axis)
10mm
• End – systole (LV short axis)
14mm
Strain calculates % thickening or shortening Strain = 14 – 10/10 = 40% Ending thickness - starting thickness / starting thickness = % strain 16
Strain Rate • Strain rate measures the time course of deformation, and is the primary parameter of deformation derived from tissue Doppler • Strain is an analog of regional function • Increased preload = increased strain • Increased afterload = reduced strain – Strain rate • Less related to pre load and after load than strain
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•The strain rate is the temporal derivative of the strain and indicates therefore the rate of the deformation. •This measurement is closely related to parameters of myocardial contractility.
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Strain and Strain Rate Imaging • Strain Imaging measures the physical change (deformation) of the myocardium • Strain Rate Imaging measures how fast the deformation of the myocardium is occurring • To assess regional myocardial function • Distinguish local velocity from translational motion • Unaffected by tethering effect from other regions • Relatively uniform throughout the normal left ventricular myocardium 19
filling
HOW TO MEASURE THE STRAIN
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Strain • • • • • • •
M Mode Tissue Doppler Imaging (pulsed wave) Color Tissue Doppler Imaging (TDI) 2D Strain Imaging – Doppler Velocity Speckle Tracking Torsion Twist 22
Why not one • Vigilance to ensure that values obtained by various techniques and technologies don’t get “lost in translation” and truth identified.
•
Standardization
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Tissue Velocity Imaging from Dopplerto Grey Scale PW-DMI 1989
2D-Color DMI
2001
Color M-Mode
2003
Strain/S-Rate
2005
Speckle tracking 2007
Speckle tracking
M mode: Real Time Acquisition of Thickening Parameters
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Tissue Doppler Imaging Techniques PW TDI
Color TDI S’
S’ A’ A’
E’
Peak Velocities
Mean Velocities
E’
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Tissue Doppler Imaging Techniques PW TDI
Color TDI S’
S’ A’
E’
systole
E’
A’
diastole
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1.
TDI characterizes the low velocity, high intensity signals that come from the wall.
2.
TDI is limited to movement relative to the sample volume fixed in space 3.Velocity pitfalls of tethering and translational motion
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Strain Derived from Tissue Velocities • TV is maximum at the base (V1), lower in the mid heart (V2) and least at the apex (V3). • This gradient in velocities is used to calculate strain rates. • Strain rate is calculated as the difference between 2 tissue velocities along the ultrasound beam (V2 –V1) normalized to the distance between these 2 velocities 29 (d).
Higher Frame Rate with PW-DMI and M-Mode DMI Temporal Resolution 3-5 msec Q-S: Q-PEAK: ET: IRT: ICT: DIAST: C-O:
7 msec
Sutherland Doppler Myocardial Imaging Book Hasselt Belgium 2006
14 msec
85
msec
140 msec 287 msec 53 msec 67 msec 590 msec 447 msec
28 msec
50 msec
Sutherland Doppler Myocardial Imaging Book
Color Tissue Doppler Imaging (TDI)
direction and velocity
• Doppler based • Angle dependent • Difficulty lining up to scan plane • Tethering • Signal noise • Not as reproducible as anticipated
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• • • • •
High frame rate > 140 Reduce depth and sector width. Focus on temporal resolution. The angle of icidence < 15 one-dimensional
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ANGLE DEPENDENCY OF TDI •
Doppler signal is analyzed only along the scanline
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Measured velocities are understimated if us beam is not adequately aligned with the movement direction of the examined structure
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Narrow sector single wall acquisition may help minimizing this problem
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3 components of myocardial motion can be interrogated by Doppler techniques
Longitudinal Radial Cinrcumferential
Velocity: traslocation ,rotation ,thetering
Galiuto et al. EAE Textbook on Echocardiography. (in press) ed. Oxford: Oxford University Press; 2010
Tissue Based Strain Doppler TIPS • • • • •
To assess motion in a base to apex direction Sensitive to sub endocardial damage Velocity regression technique Signal noise ensure clean velocity signal Angle dependence align axis of movement with scan line + narrow sector. • Respiratory drift acquire end expiration • Underestimation use high frame rates • Plane motion Caution in interpretation of events late after QRS 34
Onset to Peak Systole Septum Lateral
Systolic Ejection Time
Onset ECG Q-wave 35
Optimal Image Capture
Similar heart rate
LVOT for marking ET 36
Figure 3. Example of longitudinal velocity and strain curves before and after induction of a myocardial infarction. The basal portion of the interventricular septal wall (yellow curve) is necrotic whereas the mid (blue curve) and apical (red curv...
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In Review • Tissue Doppler based strain – The velocity movement of the myocardium – Displayed as a parametric color image – Each pixel represents velocity relative to the transducer – Graphically recorded – Regression gradient between two points of velocity data, this measure provides the shortening or lengthening that represents strain 38
2D Based Strain Speckle Tracking
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Doppler Strain – Primary Data is Strain Rate Frame 1
Frame 2
Frame 3
•Acquire a cineloop of Colour DTI /TVI • Unpack each frame •Offline analysis •Pixel encoded velocity data •High spatial resolution velocity map
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Doppler Strain â&#x20AC;&#x201C; Primary Data is Strain Rate Frame 1
Frame 2
Frame 3
1cm
V1
V2
4cm/s - 5cm/s 1cm The Prince Charles Hospital
SR = v 2 - v1 Distance x
= -1/s GMS2012
Doppler Strain â&#x20AC;&#x201C; Primary Data is Strain Rate -1/s
Frame 1
Frame 2
Frame 3
1cm
V1 5cm/s
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V2 - 7cm/s 1cm
= -2/s GMS2012
Doppler Strain â&#x20AC;&#x201C; Primary Data is Strain Rate -1/s
Frame 1
-2/s
Frame 2
Frame 3
1cm
V1 5cm/s
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V2 - 5cm/s 1cm = 0/s
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Doppler Strain â&#x20AC;&#x201C; Primary Data is Strain Rate -1/s
Frame 1
-2/s
0/s
Frame 2
SR = v 2 - v1 Distance x
V1 Frames
V2 E IVC
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Frame 3
A
IVR
[1/s]
Time Strain Rate
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Pros & Cons 2D Strain Advantages
High spatial resolution Not Doppler angle dependant Analyses strain in 3 axis directions
Disadvantages
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Extremely image dependant Offline only Low temporal resolution
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Speckle Tracking Techniques • • • •
Ultrasound reflectors within the tissue Highly reproducible Behave like magnetic resonance tags Shortening can be calculated by comparison of speckles from frame to frame • Attention to technical detail important, high frame rates can create high noise level
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Competing technologies for Strain Doppler Strain
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2D Strain
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Optimal Image Capture
High frame rates Heart rates similar 48
Derivation of 2D Strain by Echo ZOOM
ZOOM
BLOCK
Y
New location Old location
dY 0
dX
X
Leitman M et al. JASE 2004; 17:1021-1029 49
Longitudinal Strain Normal
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Longitudinal Strain Rate Normal
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Radial Strain Short Axis
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Radial Displacement
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Clinical Applications Apex
Regional Function
Left Ventricular Function
Intramural Function
CRT
LAA Function
Right Ventricular function
LeftAtrial Function
Global Strain
Trambaiolo P Salustri A, JASE
Longitudinal Strain Dilated Cardiomyopathy
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Follow-Up: Myocarditis Before recovery
European Society of Cardiology copyright -All right reserved
After recovery
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Courtesy of Dr. M. Feinberg
Global LV Function • Global LV Function traditionally measured by LVEF and Volumes • Regional Wall Function – Highly subjective – Desires high level of training
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Abnormal Global Longitudinal Strain â&#x20AC;&#x201C; 14%
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Inferior yellow
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Acute MI Typical Patterns Normal
LAD
RCA
LCX
European Society of Cardiology copyright -All right reserved
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2D Speckle Tracking to Calculate Strain in Infarction
Bullâ&#x20AC;&#x2122;s eye plots generated by semiautomated strain analysis using 2dimensional speckle tracking technique to calculate strain
A : Normal Volunteer B: Antero-lateral infarction C: Infero-lateral Infarction D: non ischemic cardiomyopathy
Abraham TP et al Circulation 2007; 116: 2597-2609
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Normals (n=40)
165±61
*p<0.001
STRAIN % Atrial Fibrillation (n=68)
79±16 98±31
44±26*
26±21* 26±18*
Strain
Normal subject
Patient with amiloidosys
3D Displacement
Limitations of 2D Speckle Tracking Hypertrophic Cardiomyopathy
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The optimal frame rate for speckle tracking seems to be 50-70 frame per seconds which is lower compared to TDI(>180 frame).this could result in undersampling especially in patients with tachicardia
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Rapid events during the cardiac cycle (ICT,IVRT) may disappear all together and peak SR and vel values may be reduced due to under sampling especially in isovolumic phases and in early diastole
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Calculated parametres are averaged over the myocardial segment when using the result page of the software.
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Small regions of myocardial dysfunction such as early stages of hypertrophic cardiomyopathy or arrhythmogenic right ventricular dysplasia the averaging could result in normal deformation
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Software programs designed for speckle tracking are new and are subjected to periodical improvment
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Different tracking algorithms produce different results
Right Ventricular Dysplasia
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So Why Is Strain Rarely Used? • In 2012 very few echoes report any advanced mechanics
• No interoperability – Each company has proprietary format – No DICOM scan line format – Different results with different equipment
• Need for standardization phantom • Changing workflow requirements – On-line or off-line? Need for separate review software?
• Too many parameters! – Need for comparative studies 66
TDI versus STE strain STE STRAIN
TDI STRAIN • 1-dimensional
• 2-dimensional
• Angle-dependent (limited segments)
• Angle-independent (comprehensive)
• Limited spatial resolution
• Better spatial resolution
• High temporal resolution
• Lower temporal resolution
• Less dependent on image quality
• Dependent on image quality
• Requires expert readers to ensure
• Semi-automated analysis for less
reliability of results
experienced observers
• Time consuming
• Rapid
• Higher interobserver reproducibility
• Better reproducibility 67
Difference between Myocardial Velocity by Doppler and by Speckle tracking • Higher frame rate • Great experience in many studies • Angle Dependence • Higher temporal resolution
Doppler
• No angle dependence • Possibility to analyze the apex • Better lateral resolution 2D Speckle • More automated and applied • More reproducible • Usable on previous exams stored(Grey scale) 68
Thank You!
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