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Special Topic In Cardiac MR Imaging
Medical Imaging & Image Processing Lab
M I I P
Center for Informatics ScienceNile University, Egypt
Abdallah G. MotaalResearch Assistant,
MSc. Candidate
Nile University, Egypt
LayoutLayout
• Background
• Cardiac Magnetic Resonance Imaging
• Strain Encoded Imaging
Theory
Anatomy Image Enhancement
Strain values correction
Background• Magnetic resonance imaging (MRI) is a safe,
noninvasive imaging technique that creates detailed images of organs and tissues.
• MRI uses radio waves and magnets to create images of organs and tissues, unlike computed tomography or conventional x rays,
MRI imaging does not use ionizing radiations.
MR Cardiac Imaging• Cardiac MR is used to image the heart while it is
beating, producing both still and moving pictures of the heart and major blood vessels.
• Cardiologists use cardiac MR to get images and to look at the structure and function of the different region of the heart. These images can help them decide how best to treat patients with heart problems.
Cardiac Imaging (2)• Cardiac MRI is a common test for diagnosing
and evaluating a number of diseases and conditions, including:
Coronary artery disease Heart valve problems Congenital heart defectsCardiomyopathiesCardiac Tumors
Image with a cardiac infarction
What is SENCWhat is SENC• SENC is a technique that is used to quantify regional
function of heart by direct encoding of regional strain of the heart into the acquired image.
• The technique measure the strain in the direction orthogonal to the image plane.
• Therefore, in case of short-axis images, only the longitudinal compression of the myocardium from base to apex is measured. On the other hand, circumferential shortening of the myocardium can be measured in the long-axis views of the heart (such as the four-chamber view).
Short Axis
Theory• Tagging– Tags are temporary non-invasive markers
whose deformations follow the motion of underlying tissue.
Diastole Systole Diastole Systole
Cardiac image before and after applying SPAMM tagging
Theory (2)• Tagging is done in the direction parallel to the image plane.• During cardiac cycle, these tag lines follow the motion of the
heart.
• So by knowing the change in the tagging frequency we can get the change in length, so we can calculate the strain.
Before Contraction After Contraction
Theory (3) Because of stretching and contraction of the heart, the tagging
frequency ranges from wl and wh.
Because of the contraction of the heart, the tagging frequency will change.
-wl wl 0 wh -wh
S(w)
M(z)
MyocardiumStatic Tissue
Color Mapping
• The normal longitudinal strain ranges from 5 to -25.• For qualitative assessment, strain values are represented by
colors.
5
-25
Time
Simulator
Time
% Strain
• By adding both the L.T and H.T we will get an informative anatomical Image. But the elevated noise leads to poor contrast to noise ratio(CNR).
Anatomy Image Enhancement
• Bayes classifier was used to increase the CNR.Based on statistical model of both background and
tissue signal
A. Motaal, M. Al-Attar, N. Osman ,A. Fahmy
CIBEC ’ 08IEEE Proceedings
Interleaving Strain Error Correction
T SecondsT Seconds
The Total Time Taken is 2*T Seconds
T Seconds
The Total Time Taken is only T Seconds
Non - InterleavedNon - Interleaved
InterleavedInterleaved
One-heartbeat Interleaved SENC Sequence
trigger
Problem: interframes motion of the heart
. . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Correction AlgorithmCorrection Algorithm
w1 w2 w3 W nWn-1
Estimate w
DerivativeDerivative
Diff < β
Compare Wn-1
Compare Wn-1
NO
Yes
STOP
Proposed Correction Algorithm
Phantom Experiment
• Numerical Computer Simulation was done to generate SENC images with different strain curves, and the proposed algorithms were tested on them
After CorrectionBefore Correction`
Time FrameTime Frame
Stra
in
Stra
in
Results
Results (cont.)
SummarySENC is a technique for measuring regional
function of the heart.We developed a Bayesian method to improve
the anatomical image reconstructed from SENC.
We propose an algorithm to correct strain measurements in interleaved acquisition.
The technique enables the reduction of the required timeframes; hence, faster and better quality imaging.
