Practical recommendations
M. Neuss, B. Schnackenburg
Scar imaging
The principle behind scar imaging is the different distribution volume and the different distribution kinetic of gadolinium-based contrast
agents in scar tissue versus normal myocardium. If measured at the appropriate time with
the appropriate imaging sequence, the high concentration of contrast agent in scar tissue results in a signal of high intensity from the scar,
intermediate intensity from the blood and low
intensity from normal myocardium. The imaging technique uses a 1808 inversion pre-pulse.
During the recovery of the magnetisation the
signal is read out at a time when the myocardial
signal is zero or very low. The zero crossing
time for the myocardium depends on many parameters like dosage of the contrast-agent, time
after the application of the contrast-agent and
physiological parameters. Therefore it is necessary to estimate the zero crossing point, which
will be used as pre-pulse delay for each patient.
As for the dose of contrast agent required for
scar imaging, dosages in the literature vary. In
the most recent studies most commonly a single
dose of contrast agent (0.1 mmol/kg body
weight) was used. In our hands the application
of a double dose results in a better contrast between blood, scar tissue and myocardium, especially when used in combination with perfusion
imaging. This advantage is partly offset by the
higher cost of the double dose of contrast agent.
At a concentration of 0.5 M the amount of contrast agent for a single dose corresponds to
0.1 ml/kg body weight.
Scar imaging in principle can be combined
with most other MR examinations of the heart,
but sometimes the timing of the application of
the contrast agent is critical. If the contrast
agent is applied at the beginning of the examination and an intricate regional wall motion
analysis is necessary this is often precluded because the application of the contrast agent decreases the contrast between blood and myocardium. On the other hand, to apply the contrast
agent after the remainder of the examination
has been terminated prolongs the total time of
the examination by another 15 min. It is, therefore, important to apply the contrast agent at a
time when the reduced blood-myocardium contrast does not interfere with vital parts of the
examination anymore without adding too much
time to the examination.
n Scan procedure
1. Basic LV anatomy, extended protocol if major
regional wall motion abnormality or at least
moderately reduced global LV-function.
2. Apply contrast agent (see above).
3. Copy geometry of SA, 4ch, 3ch, 2ch. Use inversion prepared 2D- or 3D-T1 weighted Gradient Echo sequence. We use 2 stacks of
slices (10 mm) to cover SA, 1 stack (10 mm)
to cover each 4ch, 3ch, 2ch.
4. Wait 10 min after application of contrast
agent.
5. Use a “pre-pulse delay finder” sequence, like
inversion prepared ultrafast CINE sequence.
If not available, use 3 single slice sequences
with readout after inversion-pre-pulse:
225 ms, 250 ms, 275 ms. Use pre-pulse timing
that gives lowest myocardial signal.
6. Enter retrieved pre-pulse timing into scan
planned under 3.
7. Acquire images in expiration.
8. If image quality insufficient, repeat pre-pulse
finder and scan.
n Problems
n Pre-pulse destroys ECG. If myocardial signal
is low, triggering and nulling of the myocardium worked regardless, use images. If myocardium appears in shades of grey, pre-pulse
is wrong. Repeat in different breathhold position.
n Myocardium appears grey with dark black
epicardial and endocardial lines. Imaging artefact, read out is too early, add 10–15 ms to
time after pre-pulse.