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Assessment of 4D-MRI for Robust Motion and Volume Characterization

C Glide-Hurst

C Glide-Hurst1*, J Kim1 , Y Hu2 , N Wen1 , S Mutic2 , I Chetty1 , (1) Henry Ford Health System, Detroit, MI, (2) Washington University in St Louis, St Louis, MO


TH-A-BRF-12 Thursday 7:30AM - 9:30AM Room: Ballroom F

Purpose: Precise radiation therapy for abdominal lesions is complicated by respiratory motion and poor soft tissue contrast from 4DCT whereas 4D-MRI provides superior tissue discrimination. We evaluated a novel 4D-MRI algorithm for MR-SIM motion management.

Methods: Respiratory-triggered, T2-weighted single-shot Turbo Spin Echo 4D-MRI was evaluated for open high-field 1.0T MR-SIM. A programmable platform pulled objects on a trolley ~2 cm superior-inferior (S-I) for “regular” (sinusoidal, (1-cos²), 3-5 second periods) and “irregular” breathing patterns (exaggerated (1-cos²) and patient curves), while a respiratory waveform was generated via a pressure sensor device. Coronal 4D-MRIs (2-10 phases, TE/TR/α = 35-61/6100 ms/90°, voxel=1x1x4 mm³) were acquired for 54 unique phantom cases. Abdominal 4D-MRIs were evaluated for 5 healthy volunteers and 1 liver cancer patient (6-10 phases, TE/TR/α = 30-96/4500-6100 ms/90°, voxel=1x1x5-10 mm³) on an IRB-approved protocol. Duty cycle, scan time, and excursion were evaluated between phase acquisitions and compared to coronal cine-MRI (~1 frame/sec). Maximum intensity projections (MIPs) were analyzed.

Results: In phantom, average duty cycle was 42.6 ± 11.4% (range: 23.6–69.1%). Regular, periodic breathing (sinusoidal, (1-cos²)) yielded higher duty cycles than irregular (48.5% and 35.9%, respectively, p<0.001) and fast periods had higher duty cycles than slow (50.4% for 3s and 39.4% for 5s, p<0.001). ~4-fold acquisition time increase was measured for 10-phase versus 2-phase. MIP renderings revealed that S-I object extent was underestimated a maximum of 4% (3mm) and 8% (6mm) for cine and 2-phase 4D-MRI, respectively, with respect to 10-phases. However, this was waveform dependent. A highly irregular breathing volunteer yielded lowest duty cycle (23%) and longest 10-phase scan time (~14 minutes), although 6-phase acquisition for a liver cancer patient was reasonable (50% and 7.4 minutes, respectively).

Conclusion: 4D-MRI offers potential for excursion characterization, although results suggest the use of adequate phases is important. Further application and clinical validation are warranted.

Funding Support, Disclosures, and Conflict of Interest: Research supported in part by a grant from Philips HealthCare (Best, Netherlands) and an Internal Mentored Grant from Henry Ford Health System.

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