title: Impact of incorporating visual biofeedback in 4D MRI.
abstract: Precise radiation therapy (RT) for abdominal lesions is complicated by respiratory motion and suboptimal soft tissue contrast in 4D CT. 4D MRI offers improved con-trast although long scan times and irregular breathing patterns can be limiting. To address this, visual biofeedback (VBF) was introduced into 4D MRI. Ten volunteers were consented to an IRB-approved protocol. Prospective respiratory-triggered, T2-weighted, coronal 4D MRIs were acquired on an open 1.0T MR-SIM. VBF was integrated using an MR-compatible interactive breath-hold control system. Subjects visually monitored their breathing patterns to stay within predetermined tolerances. 4D MRIs were acquired with and without VBF for 2- and 8-phase acquisitions. Normalized respiratory waveforms were evaluated for scan time, duty cycle (programmed/acquisition time), breathing period, and breathing regularity (end-inhale coefficient of variation, EI-COV). Three reviewers performed image quality assessment to compare artifacts with and without VBF. Respiration-induced liver motion was calculated via centroid difference analysis of end-exhale (EE) and EI liver contours. Incorporating VBF reduced 2-phase acquisition time (4.7 ± 1.0 and 5.4 ± 1.5 min with and without VBF, respectively) while reducing EI-COV by 43.8% ± 16.6%. For 8-phase acquisitions, VBF reduced acquisition time by 1.9 ± 1.6 min and EI-COVs by 38.8% ± 25.7% despite breathing rate remaining similar (11.1 ± 3.8 breaths/min with vs. 10.5 ± 2.9 without). Using VBF yielded higher duty cycles than unguided free breathing (34.4% ± 5.8% vs. 28.1% ± 6.6%, respectively). Image grading showed that out of 40 paired evaluations, 20 cases had equivalent and 17 had improved image quality scores with VBF, particularly for mid-exhale and EI. Increased liver excursion was observed with VBF, where superior-inferior, anterior-posterior, and left-right EE-EI displacements were 14.1± 5.8, 4.9 ± 2.1, and 1.5 ± 1.0 mm, respectively, with VBF compared to 11.9 ± 4.5, 3.7 ± 2.1, and 1.2 ± 1.4 mm without. Incorporating VBF into 4D MRI substantially reduced acquisition time, breathing irregularity, and image artifacts. However, differences in excursion were observed, thus implementation will be required throughout the RT workflow.
authors.affiliation: Henry Ford Health System. DTO1@hfhs.org.
authors.forename: David T
authors.initials: DT
authors.lastname: To
authors.forename: Joshua P
authors.initials: JP
authors.lastname: Kim
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Price
authors.forename: Indrin J
authors.initials: IJ
authors.lastname: Chetty
authors.forename: Carri K
authors.initials: CK
authors.lastname: Glide-Hurst
mesh_terms: D000328:Adult; D001676:Biofeedback, Psychology; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008099:Liver / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D009068:Movement; D011857:Radiographic Image Interpretation, Computer-Assisted; D012119:Respiration; D059629:Signal-To-Noise Ratio; D014796:Visual Perception; D055815:Young Adult