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العنوان
Is There a Role For Diffusion Based MRI Sequences in Evaluation and characterization of Myocardial Infarction?/
المؤلف
Amer, Mohamed Ali Sayed.
هيئة الاعداد
مشرف / Omar Hussein
مشرف / Ahmed Samir Ibrahim
مناقش / Nivine Chalabi
مناقش / Nivine Chalabi
تاريخ النشر
2014.
عدد الصفحات
185p. :
اللغة
الإنجليزية
الدرجة
ماجستير
التخصص
الإشعاع
تاريخ الإجازة
1/1/2014
مكان الإجازة
جامعة عين شمس - كلية الطب - اشعة تشخيصية
الفهرس
Only 14 pages are availabe for public view

from 185

from 185

Abstract

Cardiovascular magnetic resonance (CMR) imaging is a
great advancement in the field of health care, which has
emerged as an important clinical technique in the diagnosis,
therapeutics and prognostication of IHD. Early and accurate
diagnosis of acute myocardial infarction (MI) is necessary for
optimizing management of patients with acute MI and for
improving outcome.
Magnetic resonance (CMR) new pulse sequences have got
the inherently superior soft tissue contrast provided by MR, so
that it now provides the reference standard for in vivo
viability imaging as well as the assessment of regional and
global systolic function, the detection of myocardial infarction
and viability and the evaluation of pericardial disease and
cardiac masses.
Evaluation of AMI (acute myocardial infarction) with
magnetic resonance imaging, allows detection of reversible
and irreversible injury of the myocardium. Cardiovascular
Magnetic Resonance (CMR) in one examination provides an
accurate assessment of myocardial function and morphology
(edema, impaired microcirculation, hemorrhage, and
necrosis).
Therefore, CMR has great potential as a diagnostic
method in the acute phase of myocardial infarction, providing
information on the degree and extent of reversible and
irreversible myocardial damage.
STIR sequences are commonly applied to detect
myocardial edema, combined with Late Gadolinium
Enhancement (LGE); STIR images allow the quantification of
myocardial salvage index and to distinguish between acute
and chronic injuries.
Despite all the advantages of STIR imaging, this
technique has some limitations; the main shortcomings of this
technique are motion artifacts, Partial blood suppression in
the area of slow flow leading to a “slow flow artifact” which
is often confused with sub-endocardial edema. Moreover
Dark-blood preparation pulse may also cause a significant
signal loss and variations, which may result in an incorrect
diagnosis.
Diffusion weighted imaging is a new technique for edema
detection in patients with acute myocardial infarction and has
higher sensitivity in the detection of myocardial edema than
STIR. The sensitivity of the DWI sequence, in contrast to the
STIR, does not depend on the infarct location, provides total
suppression of the blood signal and reduces the occurrence of
motion artifacts. So it may be recommended for the diagnosis
of acute injuries, especially in patients with “slow-flow”
artifacts in STIR images.
As early and accurate diagnosis of acute myocardial
infarction (MI) is necessary for optimizing management of
patients with acute MI and for improving outcome. DWI was
able to show myocardial involvement in 78% of MI patients
in less than 1 min acquisition time, with a similar extent
assessment as late-gadolinium enhancement sequence. The
most important issue is that MI detection with DWI rose to
97% for recent MIs, despite not discriminating from subacute
MIs. The earlier is the MR examination after the cardiac
event, the better should be the sensitivity of DWI.
Diffusion tensor magnetic resonance imaging (DT-MRI) has
emerged as a candidate method for nondestructive reconstruction
of the fiber structure of the left ventricle and reflect the structural
integrity of underlying tissues.
It is crucial to investigate the sequential changes of myocardial
microstructure and its relationships with changes of macrostructure
and function of the left ventricle post-MI; this can be achieved by
Diffusion tensor magnetic resonance imaging (DT-MRI).
Diffusion spectrum MRI tractography (DSI tractography), is a
novel complex technique that was experimented ex-vivo to image
myofiber architecture in normal and infarcted myocardium. It
resolves multiple myofiber populations per voxel, with the ability
to describe fiber crossings.
DSI tractography reveals a complex network of orthogonal
myofibers within infarcted myocardium which may resist
mechanical remodeling but also probably increase the risk for
lethal reentrant arrhythmias.
Diffusion based MRI sequences had some limitations as it is
not yet able to discriminate between MI and acute myocarditis , it
did not focus on transmurality of the DWI hypersignal . It cannot
be excluded that DWIs provided some false positive results due to
the bulk motion artifact.
CMR has great potential and as a diagnostic method in the
acute phase of myocardial infarction, providing information on the
degree and extent of reversible and irreversible myocardial
damage.
Diffusion weighted imaging (DWI) sequence are sensitive to
the increase of water content in the myocardium and may be used
as an alternative or in addition to the standard T2- STIR weighted
sequences as it raised the MI detection to 97% for recent MIs.
The new MR acquisition technique reducing substantially
diagnostic imaging times by allowing prompt diagnosis of cardiac
ischemic disease should help a better triage of emergency patients,
by comparison with biochemical markers such as troponin, the
raise of which being frequently delayed by 8 h.
Understanding the altered tissue integrity and fiber architecture
in diseased myocardium such as myocardial infarction (MI) is
critically important because it might shed light on the mechanism
of structure-function remodeling after MI. this can be assessed by
using DWI .
Cardiac DT-MRI can is used to estimate infarct size and a
high-resolution viability map is used for zonal segmentation of the
infarct, adjacent, and remote zones. It reflects the structural
integrity of underlying tissues.