title: Investigating the feasibility of rapid MRI for image-guided motion management in lung cancer radiotherapy.
abstract: Cycle-to-cycle variations in respiratory motion can cause significant geometric and dosimetric errors in the administration of lung cancer radiation therapy. A common limitation of the current strategies for motion management is that they assume a constant, reproducible respiratory cycle. In this work, we investigate the feasibility of using rapid MRI for providing long-term imaging of the thorax in order to better capture cycle-to-cycle variations. Two nonsmall-cell lung cancer patients were imaged (free-breathing, no extrinsic contrast, and 1.5 T scanner). A balanced steady-state-free-precession (b-SSFP) sequence was used to acquire cine-2D and cine-3D (4D) images. In the case of Patient 1 (right midlobe lesion, ~40 mm diameter), tumor motion was well correlated with diaphragmatic motion. In the case of Patient 2, (left upper-lobe lesion, ~60 mm diameter), tumor motion was poorly correlated with diaphragmatic motion. Furthermore, the motion of the tumor centroid was poorly correlated with the motion of individual points on the tumor boundary, indicating significant rotation and/or deformation. These studies indicate that image quality and acquisition speed of cine-2D MRI were adequate for motion monitoring. However, significant improvements are required to achieve comparable speeds for truly 4D MRI. Despite several challenges, rapid MRI offers a feasible and attractive tool for noninvasive, long-term motion monitoring.
authors: University of Texas, Southwestern Medical Center, Dallas, TX 75235, USA.
authors: Amit
authors: 0000-0002-3275-4160
authors: A
authors: Sawant
authors: University of Sydney, Sydney, NSW 2006, Australia.
authors: Paul
authors: P
authors: Keall
authors: Stanford University, Stanford, CA 95305, USA.
authors: Kim Butts
authors: KB
authors: Pauly
authors: Stanford University, Stanford, CA 95305, USA.
authors: Marcus
authors: M
authors: Alley
authors: Stanford University, Stanford, CA 95305, USA.
authors: Shreyas
authors: S
authors: Vasanawala
authors: Stanford University, Stanford, CA 95305, USA.
authors: Billy W
authors: BW
authors: Loo
authors: University of Utah, Salt Lake City, UT 84112, USA.
authors: Jacob
authors: J
authors: Hinkle
authors: University of Utah, Salt Lake City, UT 84112, USA.
authors: Sarang
authors: S
authors: Joshi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D061089:Radiotherapy, Image-Guided; D012119:Respiration; D014057:Tomography, X-Ray Computed