Radiation and Cancer Physics

SS 37 - Physics 11 - Online Imaging and Motion Management

268 - Inter- and Intra-Patient Peristaltic Motion Assessed With Cine-MRI

Wednesday, October 24
11:40 AM - 11:50 AM
Location: Room 302

Inter- and Intra-Patient Peristaltic Motion Assessed With Cine-MRI
F. Mostafaei1, A. Tai1, Q. Liu1, E. S. Paulson1, W. A. Hall2, B. A. Erickson1, and A. Li1; 1Medical College of Wisconsin, Milwaukee, WI, 2Medical College of Wisconsin and Clement J Zablocki VA Medical Center, Milwaukee, WI

Purpose/Objective(s): Peristaltic motion is independent of respiratory motion and can significantly affect radiation therapy (RT) delivery for abdominal cancers. MRI-guided delivery technology, allows acquisition of high resolution MRI, including 2D cine, prior to and during RT delivery. In this study, we evaluate peristalsis based on cine MRI.

Materials/Methods: A total of 33 cine MRI sets acquired during RT simulation and select fractions for 10 patients with pancreatic cancer were analyzed. Several fast, orthogonally-positioned, 2D cine MRI were acquired in sagittal, coronal and axial planes for each patient. Free breathing (FB) cine-MRI acquired during MRI simulation from 4 patients (time duration of 1.7 min, 1 second acquisition time per slice), and FB cine-MRI acquired using MR-Linac from 6 patients in various fractions (acquisition time is less than 0.6 seconds per slice) were analyzed. Motions of various organs including gallbladder (GB) and liver were measured based on these cine MRI data. The GB motion includes both respiration and peristalsis, while liver motion is primarily respiration. By subtracting liver motion (respiration) from GB motion (respiration and peristalsis), the peristaltic motion, along with small residual motion, was obtained.

Results: From 2D cine-MRI acquired during MR simulation, the residual motion beyond the respiratory motion in 1.7 min was found to be up to 6 mm in superior-inferior (SI) and 5.5 mm in anterior-posterior (AP) directions. From 2D cine-MRI acquired by the MR-Linac, different peristaltic motions were found from different fractions for each patient. The peristaltic motion was found to vary between 3-10 mm. The peristaltic motion for one patient is shown in the table. For each patient the respiratory motion pattern from GB and liver in different fractions were found to be similar, however, after subtraction, the motion pattern and amplitude were found to be different in each fraction. This indicates the non-periodic and non-predictable nature of the peristaltic motion.

Conclusion: The motion of abdominal organs due to peristalsis is substantial (up to 10 mm) and the pattern of the motion is complex compared to the respiratory motion based on 2D cine MRI. The motion can vary day to day for a given patient and can be irregular and persistent throughout RT imaging and delivery. Management of peristaltic motion, in addition to respiratory motion, should be considered in high precision RT for abdominal tumors.
2D Cine-MRI (FB) Acquired by MR-Linac 2D Cine-MRI (FB) Acquired by MR-SIM
Acquisition Time per frame 0.6 Seconds 1 Seconds
First fraction SI Liver: 10 mm GB: 11 mm Peristalsis: 3 mm Liver: 13 mm GB: 12 mm Peristalsis: 6 mm
Second fraction SI Liver: 13 mm GB: 16 mm Peristalsis: 4 mm
Third fraction SI Liver: 8 mm GB: 10 mm Peristalsis: 10 mm
Fourth fraction SI Liver: 18 mm GB: 14 mm Peristalsis: 6 mm

Author Disclosure: F. Mostafaei: None. A. Tai: None. W.A. Hall: None. B.A. Erickson: Employee; ProHealth Care, Waukesha, WI. Steering committee; American Brachytherapy Society. A. Li: None.

Farshad Mostafaei, PhD

Disclosure:
No relationships to disclose.

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