Practical recommendations
M. Neuss, B. Schnackenburg
Coronary arteries
Imaging of the coronary arteries is still experimental for most applications, but probably newer faster imaging techniques and the advent of
intravascular contrast agents will open the field
in the near future. The purpose of this paragraph is to give a brief introduction into the
imaging of coronary arteries.
Two fundamental movements of the heart
limit the time available for the imaging of the
coronaries. One is the craniocaudal movement
of the heart due to the respiratory motion of
the diaphragm, the other the rotational and the
translational movement of the heart due to its
contraction and relaxation. The use of navigators that track the movement of the diaphragm
permit to limit the acquisition of images to
identical positions of the diaphragm during free
breathing. High resolution cine-images of the
heart allow the determination of the rest period
of the coronaries. Limiting the image acquisition to identical diaphragm positions during
free breathing and to the coronary rest period
during consecutive heart beats should in principle result in MRI of the coronaries with high
vessel sharpness.
n Scan procedure
1. Use planning of basic LV anatomy.
2. Cine 4 chamber (4ch), SSFP with 40 phases.
Analyze for coronary rest period, note beginning and duration.
3. Transversal scout in SSFP technique, parallel
imaging technique, Turbo Gradient Echo
multi-shot, fat suppression, T2-pre-pulse, navigator gated. Navigator window 10 mm, slice
thickness 2–2.5 mm, 40–50 slices covering
the entire heart, enter beginning of coronary
rest period as trigger delay into scan. Nominal scan time between 1 min 30 and 2 min,
real scan time depends on gating efficiency.
Spatial resolution 1.5 ´ 1.5 ´ 2.5 mm (M/P/S).
4. Use transversal scout for planning of coronary scan in SSFP technique, parallel imaging
technique, foldover suppression, TFE multishot, fat suppression, T2-pre-pulse, navigator
gated. Navigator window 5 mm, slice thickness 0.7–1.0 mm, 15–25 slices covering one of
the coronaries, enter beginning of coronary
rest period as trigger delay into scan. Spatial
resolution 0.5 ´ 0.5 ´ 1.0 mm (M/P/S).
5. One scan for each coronary, enter beginning
of coronary rest period. Stack needs to cover
proximal, medial and distal segment of each
coronary. Nominal scan time for each coronary should not exceed 2 min 30.
n Problems
n Scanning takes too long. No easy solution to
this problem since time available for imaging
is limited by movement of both the diaphragm and the coronaries. Gating efficiency
of 20–30% is very good, below 10% unacceptable and should result in stopping and restarting the scan. Increasing the size of the
navigator window to 7 mm results in unacceptable deterioration of image quality.
n Pulsation artefacts: Either from the cerebrospinal liquor or the aorta or both. Use saturation bands to reduce extent of the problem.
n Lack in vessel sharpness: Several possible
reasons. Change in heart rate during scan results in acquisition of images while the coronary is moving. No solution if heart rate is
changing constantly. Otherwise use new scan
to determine resting period of the coronaries.
Shot duration too long: limit to 75 ms.
n It is of no use attempting coronary MRI in
patients with atrial fibrillation/flutter, frequent atrial or ventricular premature beat.