Practical recommendations
M. Neuss, B. Schnackenburg
Dilative cardiomyopathy
In the context of clinical studies and for followup it is essential to reliably determine chamber
volumes and ejection fraction. The use of scar
imaging in many cases suggests the presence of
coronary artery disease in patients formerly diagnosed as suspected dilative cardiomyopathy.
n Scan procedure
1. Follow planning as outlined in basic anatomy,
use extended protocol.
2. In case of reduced right ventricle (RV) function, determine long axis of RV. If not parallel to long axis of left ventricle (LV), cover
RV in cine SSFP from apex to base, perpendicular to long axis of RV.
3. To determine stroke volume, do flow measurement in aorta 10–15 mm distal to the
aortic valve. Use 3chamber (3ch) for planning, orthogonal to flow direction in aorta,
correct angulation in coronal image from survey. Flow velocity 200 cm/s. After acquisition
of images, check whether aorta appears
round and for absence of aliasing. If oval,
correct angulation; if aliasing present, adjust
maximal flow velocity.
4. Use scan procedures 2.–8. from the scar
imaging protocol.
n Problems
n Rhythm disturbances: In atrial fibrillation/
flutter with irregular ventricular response
time required for the image acquisition increases. The reduction of the number of heart
phases (normally 25) reduces the time for
the breathhold, but reduces the accuracy of
the determination of the volumetric end systolic volume, the volumetric stroke volume
and the volumetric ejection fraction. In some
patients rhythm disturbances render the examination meaningless.
n Shortness of breath: Reduce number of
phases, use parallel imaging techniques like
sense or half scan.
n Asynchronous ventricular contraction: Calculate enddiastolic volume using Simpson’s
method from cine images, calculate stroke
volume from flow measurement in aorta. Use
stroke volume to calculate endsystolic volume
and ejection fraction.
n Arrhythmogenic right ventricular
cardiomyopathy (ARVC)
The principal appeal of CMR in this disease entity is the unique capacity of the method to
clearly identify intramyocardial fat by virtue of
fat suppressing techniques. Theoretically appealing, in many patients with suspected ARVC
MRI is difficult due to several reasons. First of
all, very often the reason for referral are rhythm
disturbances, precluding a good image quality
in many patients. Second, areas where intramyocardial fat is most likely to occur in ARVC,
surrounding the tricuspid valve, the apex of the
right ventricle and the outflow tract are areas
where in many patients epicardial fat can be
seen, either surrounding the right coronary artery or at the apex. Third, in many patients
with ARVC fatty infiltrates in the free wall of
the thinned right ventricle come close to the
spatial resolution possible using current MRI
techniques.
The second major value of CMR is the ability
to detect regional wall motion abnormalities of
the RV. However, due to the complex motion
pattern of the normal RV the differentiation between normal, mildly abnormal or severely abnormal remains difficult.
n Scan procedure
1. Use planning for basic LV-anatomy.
2. Define long axis of RV. Cine SSFP to completely cover the RV in 2ch, 3ch, 4ch, and
short-axis (SA) geometry. Visual analysis for
aneurysms, regional wall motion abnormalities.
3. Plan blackblood (BB) sequences to cover regions with wall motion abnormalities in two
orthogonal planes, i.e., hypokinesia in the
free wall of the right ventricle: use 4ch and
SA geometry to cover free wall in orthogonal
planes. In the absence of regional wall motion abnormalities cover RV in 4ch and SA
geometry with T1-w BB. Copy geometry from
cine-images.
4. Enddiastolic T1-weighted blackblood technique (T1-w BB) with the smallest possible
FOV (< 200 mm) using regional saturation
slabs to prevent foldover.
5. Repeat T1-w BB with fat suppression. If necessary, use different techniques for fat suppression.
6. Use scan procedures 2.–8. from the scar imaging protocol.
n Problems
n Rhythm disturbances: Often no good solution
since blackblood sequences are sensitive to
motion artefacts. Try to find pathological
findings in orthogonal planes. If you cannot,
there is a high likelihood they represent artefacts. The most robust technique is the inversion-recovery technique, but the diagnostic
value for this indication is not well established.
n Uncertain findings: Common in ARVC. Consider possible left ventricular involvement.
Use information available from other diagnostic procedures. Pay the greatest attention
to reducing the FOV. If foldover is a major
problem, turn off the dorsal coil elements
and use only the ventral ones.
Infiltrative disease
A great number of rheumatic diseases, storage
diseases, disorders of the metabolism like hemochromatosis or diseases leading to abnormal
deposition of proteins like amyloidosis can affect the heart. In many of these diseases the role
of cardiac MRI is only being established, but
the method has principal appeal in comparison
to other imaging modalities. Compared to echocardiography the image quality of MR is superior and not influenced by surrounding tissue
and offers sequences for tissue characterization.
Compared to cardiac catheterization and LV angiography MR allows a more detailed analysis
of wall motion, offers sequences for tissue characterization, but lacks the chance to obtain tissue samples frequently required for definitive
confirmation or exclusion of myocardial involvement.
According to our experience cardiac MRI is
ideally suited for patients with low or intermediate probability of cardiac involvement in
systemic disease to obviate or confirm the need
for more invasive studies.
n Scan procedure
1. Use planning of basic LV anatomy, extended
protocol.
2. If questionable wall motion abnormality,
use additional cine SSFP in orthogonal geometry. Visual analysis for wall motion abnormalities.
3. Plan blackblood (BB) sequences to cover regions with wall motion abnormalities in two
orthogonal planes, i.e., hypokinesia in the
free wall of the left ventricle: use 4ch and
SA geometry to cover free wall in orthogonal planes. Copy geometry from cineimages. In absence of regional wall motion
abnormalities cover LV in 4ch and SA geometry.
4. Enddiastolic T1-weighted blackblood technique (T1-w BB).
5. Enddiastolic T1-weighted blackblood technique with fat suppression.
6. T2-weighted blackblood technique (T2-w
BB).
7. Apply single dose of contrast agent. Wait 5
min.
8. Repeat T1-w BB in previous geometry. Divide TFE-pre-pulse by two, otherwise blood
will appear bright.
9. Apply single dose of contrast agent.
10. Use scan procedures 3.–8. from the scar
imaging protocol.
Technical note: The imaging technique for T1-w
BB has to be gradient-echo, since use of spinor turbospin-echo will not result in T1-weighted
contrast.
In patients with suspected cardiac involvement in hemochromatosis T2*-weighted multiecho sequences are used to calculate T2* values
for the free wall of the right ventricle, the interventricular septum and the free wall of the left
ventricle. The principle is that the presence of
iron in tissue causes susceptibility-induced relaxation that can be used to screen for the presence of iron. The diagnostic accuracy of the
method is not well established.
Hypertrophic cardiomyopathy
While the diagnosis of hypertrophic cardiomyopathy in most cases is established by echocardiography, MRI plays an important role in displaying the exact anatomy prior to surgical correction or septal ablation by alcohol injection
during cardiac catheterization. Possible other
indications are the screening of relatives with
suspected disease. Preliminary data using delayed enhancement imaging suggest added
prognostic information in this heterogenous
group of patients.
n Scan procedure
1. Use planning of basic LV anatomy (extended
protocol).
2. Visual analysis for turbulent flow in outflow
tract of left ventricle in 3ch geometry. If pres-
ent, flow measurement orthogonal to flow
turbulence, velocity setting 300–500 cm/s.
3. Use scan procedures 2.–8. from the scar imaging protocol.
n Problems
n Lack of agreement of pressure gradient as determined in echo and MRI: Gradients are dynamic, gradients in MR are measured after
an extended rest period and, therefore, usually lower than in echo.
n Clear prolapse of anterior mitral leaflet in
echo, systolic anterior movement, systolic
notch of aortic valve, neither of those visible
in MR. Consider the possibility that the pressure gradient is exercise related. Consider increasing the number of phases from 25 to 40
for better temporal resolution.