Abstract
PurposeCardiac and respiratory motion derived image artefacts are reduced when data are acquired with cardiac and respiratory synchronisation. Where steady state imaging techniques are required in small animals, synchronisation is most commonly performed using retrospective gating techniques but these invoke an inherent time penalty. This paper reports the development of prospective gating techniques for cardiac and respiratory motion desensitised MRI with significantly reduced minimum scan time compared to retrospective gating. MethodsProspective gating incorporating the automatic reacquisition of data corrupted by motion at the entry to each breath was implemented in short TR 3D spoiled gradient echo imaging. Motion sensitivity was examined over the whole mouse body for scans performed without gating, with respiratory gating, and with cardio-respiratory gating. The gating methods were performed with and without automatic reacquisition of motion corrupted data immediately after completion of the same breath. Prospective cardio-respiratory gating, with acquisition of 64 k-space lines per cardiac R-wave, was used to enable whole body DCE-MRI in the mouse. ResultsProspective cardio-respiratory gating enabled high fidelity steady state imaging of physiologically mobile organs such as the heart and lung. The automatic reacquisition of data corrupted by motion at the entry to each breath minimised respiratory motion artefact and enabled a highly efficient data capture that was adaptive to changes in the inter-breath interval. Prospective cardio-respiratory gating control enabled DCE-MRI to be performed over the whole mouse body with the acquisition of successive image volumes every 12–15 s at 422 μm isotropic resolution. ConclusionsHighly efficient cardio-respiratory motion desensitised steady state MRI can be performed in small animals with prospective synchronisation, centre-out phase-encode ordering, and the automatic reacquisition of data corrupted by motion at the entry to each breath. The method presented is robust against spontaneous changes in the breathing rate. Steady state imaging with prospective cardio-respiratory gating is much more efficient than with retrospective gating, and enables the examination of rapidly changing systems such as those found when using DCE-MRI.
Highlights
In small animal MRI, retrospective gating has become the standard means of performing steady state maintained scanning in conjunction with cardio-respiratory motion desensitisation [1,2,3]
The short TR prospective gating method reported here enables the spin system magnetisation to be maintained in the steady state indefinitely until the control signal for data acquisition that is derived from a physiological event is registered by the scanner
These images are compared with the ‘best representation’ display in the bottom row which was produced from the average of the 20 image volumes acquired using CR-gating with automatic reacquisition of respiratory motion corrupted data
Summary
In small animal MRI, retrospective gating has become the standard means of performing steady state maintained scanning in conjunction with cardio-respiratory motion desensitisation [1,2,3]. The signal modulations that persist can present as image ghosting and/or intensity modulations which make the approach unsuitable in instances that require the steady state magnetization to be held within specific and stringent limits during a fixed TR throughout the entire scan, such as variable flip angle T1 mapping and balanced SSFP In this approach, the number of inter-breath R-waves that are used for data acquisition is specified in advance. The short TR prospective gating method reported here enables the spin system magnetisation to be maintained in the steady state indefinitely until the control signal for data acquisition that is derived from a physiological event (such as an R-wave) is registered by the scanner In this implementation, a block of N k-space lines is acquired whenever the control signal for data acquisition is registered. The rapid imaging described enables the examination of changes that occur in DCE-MRI whilst maintaining good image fidelity and high throughput operation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
