title: Direct Comparison of Respiration-Correlated Four-Dimensional Magnetic Resonance Imaging Reconstructed Using Concurrent Internal Navigator and External Bellows.
abstract: To compare the image quality of amplitude-binned 4-dimensional magnetic resonance imaging (4DMRI) reconstructed using 2 concurrent respiratory (navigator and bellows) waveforms.
  
  
  
  A prospective, respiratory-correlated 4DMRI scanning program was used to acquire T2-weighted single-breath 4DMRI images with internal navigator and external bellows. After a 10-second training waveform of a surrogate signal, 2-dimensional MRI acquisition was triggered at a level (bin) and anatomic location (slice) until the bin-slice table was completed for 4DMRI reconstruction. The bellows signal was always collected, even when the navigator trigger was used, to retrospectively reconstruct a bellows-rebinned 4DMRI. Ten volunteers participated in this institutional review board-approved 4DMRI study. Four scans were acquired for each subject, including coronal and sagittal scans triggered by either navigator or bellows, and 6 4DMRI images (navigator-triggered, bellows-rebinned, and bellows-triggered) were reconstructed. The simultaneously acquired waveforms and resulting 4DMRI quality were compared using signal correlation, bin/phase shift, and binning motion artifacts. The consecutive bellows-triggered 4DMRI scan was used for indirect comparison.
  
  
  
  Correlation coefficients between the navigator and bellows signals were found to be patient-specific and inhalation-/exhalation-dependent, ranging from 0.1 to 0.9 because of breathing irregularities (>50% scans) and commonly observed bin/phase shifts (-1.1 ± 0.6 bin) in both 1-dimensional waveforms and diaphragm motion extracted from 4D images. Navigator-triggered 4DMRI contained many fewer binning motion artifacts at the diaphragm than did the bellows-rebinned and bellows-triggered 4DMRI scans. Coronal scans were faster than sagittal scans because of the fewer slices and higher achievable acceleration factors.
  
  
  
  Navigator-triggered 4DMRI contains substantially fewer binning motion artifacts than bellows-rebinned and bellows-triggered 4DMRI, primarily owing to the deviation of the external from the internal surrogate. The present study compared 2 concurrent surrogates during the same 4DMRI scan and their resulting 4DMRI quality. The navigator-triggered 4DMRI scanning protocol should be preferred to the bellows-based, especially for coronal scans, for clinical respiratory motion simulation.
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York. Electronic address: lig2@mskcc.org.
authors.forename: Guang
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Computer Science, City College of New York, New York, New York.
authors.forename: Jie
authors.initials: J
authors.lastname: Wei
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Devin
authors.initials: D
authors.lastname: Olek
authors.affiliation: Philips Healthcare, MR Therapy Cleveland, Ohio.
authors.forename: Mo
authors.initials: M
authors.lastname: Kadbi
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Neelam
authors.initials: N
authors.lastname: Tyagi
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Kristen
authors.initials: K
authors.lastname: Zakian
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: James
authors.initials: J
authors.lastname: Mechalakos
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Deasy
authors.affiliation: Department of Medical Physics, Memorial Sloan Kettering Cancer Center, New York, New York.
authors.forename: Margie
authors.initials: M
authors.lastname: Hunt
mesh_terms: D059925:Anatomic Landmarks; D016477:Artifacts; D045853:Exhalation; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D001239:Inhalation; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D009068:Movement; D011446:Prospective Studies; D012119:Respiration; D012189:Retrospective Studies