Fifty-eighth annual meeting of the american association of physicists in medicine
TH-EF-BRA-09: Direct Comparison of T2-Based Respiratory-Correlated 4DMRI Reconstructed from Simultaneous Internal Navigator and External Bellows
To optimize T2-based respiratory-correlated 4DMRI for motion simulation, we evaluated the image quality after 4D reconstruction based on the two respiratory surrogates acquired independently and concurrently during the same breathing period.
Both internal navigator and external bellows were employed simultaneously during a 4DMRI acquisition on seven volunteers scanned coronally and sagittally under an IRB-approved protocol. The navigator was positioned at the right diaphragm dome while the bellows was placed at the upper abdomen. Using the navigator as the primary surrogate, prospective amplitude-binning was used to fill respiratory bins and anatomic slices to complete the amplitud-elocation table on the fly to reconstruct a single-breath 4DMRI. Five bins in both inhalation and exhalation were used, forming a 10-bin 4DMRI. Following the same binning method, a bellows-based 4DMRI was then reconstructed retrospectively using a MATLAB programs developed for the rebinning and data analysis. The two surrogates were compared on 1D breathing waveforms and 4D image quality around the diaphragms. The waveform comparison included correlations in inhalation and exhalation, hysteresis analysis by ellipsoidal fitting, and histogram analysis for slice redistribution in bellows-based bins. Image quality comparison between the navigator-based and bellows-based 4DMRI included motion artifact visualization and phase-shift quantification at the right and left diaphragms.
The correlation between the navigator and bellows is usually higher in inhalation than exhalation. Their non-linear relationship is represented using ellipsoidal fitting with minor-to-major-axis ratio of 0.2–0.5 and by cross-correlation with phase shifts (0.2–2). Overall, navigator-based 4DMRI has superior image quality, although artifacts at anatomy distant to the navigator, such as the left diaphragm, are observed.
This is the first time that two-differently-binned 4DMRI image sets from the same breathing period have been directly compared. Navigator-based 4DMRI is generally superior to bellows-based 4DMRI, making it clearly suitable for tumor delineation in future clinical applications.
This study is in part supported by the NIH (U54CA137788/U54CA132378). Also, this research is collaborated with Philips Healthcare.