Development of algorithms for respiratory motion correction in coronary MRIECG-triggered coronary MR angiography (CMRA) has improved
under many aspects in the recent years. Free-breathing imaging
applied to this context is desirable for a number of reasons.
First, it is comfortable for the patient because it does not
require long and repeated breathholds and makes therefore
possible the examination of pediatric patients and of patients
that have difficulties in maintaining even a short breathhold.
Second, the acquisition time does not need to be constrained
to a breathhold window and can therefore be noticeably
increased. Eventually, free-breathing acquisitions are
commonly considered to be more clinically relevant than
extended breathholds, as the latter can lead to poorly
understood changes in blood flow and pressure in the region of
the heart.
The well established use of beam navigators, usually placed on
the dome of the right hemidiaphragm, features a real time
prospective tracking of the respiratory motion in the
direction of its main motion pattern; namely the Superior-
Inferior (SI) orientation. This method allows the definition
of a respiratory gating window so that the data that are
acquired outside this window are rejected and remeasured in
the following R-R interval. This kind of approach, which
assumes a linear relationship with a fixed and patient-
independent correction factor between the SI displacements of
the diaphragm and the heart, needs to make use of very small
acceptance windows - typically 5 mm - and results therefore in
a reduced scan efficiency of 30-50 % and prolonged scan times.
Even though navigator-gated techniques are generally efficient
in minimizing the artifacts caused by respiratory motion, they
bear a number of shortcomings. First, the correlation between
the measured navigator position and the actual position of the
heart might be adversely affected by hysteretic effects,
imprecise navigator positioning and temporal delays between
the navigators and the image acquisition. Second, irregular
breathing patterns may heavily worsen the scan efficieny and
prolong the exam time. Third, an extensive scout scanning
before image acquisition is required. The goal of this project is the development of algorithms for
motion detection and correction which could be intrinsically
integrated in the image acquisition and overcome the
shortcomings of the current gold standards. A minimal pre-scan
planning and maximum acquisition efficiency are desired.
| Project manager: Prof. Dr.-Ing. Joachim Hornegger, Michael Zenge Ph.D., Arne Littmann Ph.D.
Project participants: Dipl.-Ing. Davide Piccini
Keywords: Respiratory motion correction; 3D acquisition; coronary MRI
Duration: 1.12.2008 - 30.11.2011
Sponsored by: Siemens AG, Healthcare Sector
Contact: Piccini, Davide E-Mail: davide.piccini@cs.fau.de
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