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TH‐CD‐204‐01: FEATURED PRESENTATION and BEST IN PHYSICS (JOINT IMAGING‐THERAPY): Novel SG‐KS‐4D‐MRI Sequence Reduces 4D Rebinning Artifacts and Improves GTV Contouring Consistency for Pancreatic Cancer Patients
Author(s) -
Yang W,
Fan Z,
Tuli R,
Deng Z,
Pang J,
Wachsman A,
Reznik R,
Sandler H,
Li D,
Fraass B
Publication year - 2015
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4926248
Subject(s) - contouring , magnetic resonance imaging , nuclear medicine , real time mri , dynamic contrast enhanced mri , medicine , radiology , computer science , computer graphics (images)
Purpose: Dynamic magnetic resonance imaging (MRI) has been used to characterize tumor motion but real time acquisition has been limited to 2‐dimensions. Methods have been developed to reconstruct four‐dimensional MRI (4D‐MRI) based on time‐stamped 2D images or 2D K‐space data. These methods suffer from anisotropic resolution and rebinning artifacts. We have developed a self‐gating based K‐space sorted 4D‐MRI (SG‐KS‐4D‐MRI) method to overcome these limitations and in this study apply it to monitoring organ motion of pancreatic cancer patients. Methods: Ten patients were imaged using 4D‐CT, cine 2D‐MRI and the SG‐KS‐4D‐MRI method, which is a spoiled gradient recalled echo (GRE) sequence with 3D radial‐sampling K‐space projections and 1D projection‐based self‐gating. Tumor volumes were drawn at the end of exhalation phases in the 4D‐MRI and 4D‐CT, and mapped to the other phases using deformable registration. The tumor volumes and motion trajectories were compared. Results: An isotropic resolution of 1.6 mm was achieved in the SG‐KS‐4D‐MRI images, which showed superior soft tissue contrast to 4D‐CT and appeared to be free of rebinning artifacts. SG‐KS‐4D‐MRI was able to detect out‐of‐plane tumor motion and showed good correlation with 4D‐CT and cine 2D‐MRI in superior‐inferior direction with a correlation coefficient of 0.91±0.06 and 0.93±0.03, respectively. The average standard deviation of GTV (GTV_σ) calculated from ten breathing phases were 0.81 cc and 1.02 cc for SG‐KS‐4D‐MRI and 4D‐CT (p=0.004) respectively. Conclusion: A novel SG‐KS‐4D‐MRI acquisition method capable of reconstructing rebinning‐artifact‐free high resolution 4D‐MRI images was used to quantify pancreas tumor motion. The resultant pancreatic tumor motion trajectories better agreed with 2D‐cine‐MRI and 4D‐CT in the SI direction than the other 2 directions due to smaller motions in those directions. The pancreatic tumor volumes derived using SG‐KS‐4D‐MRI were significantly more consistent than those from the 4D‐CT.This work is supported in part by NIH grant 1R03CA173273‐01. This study is supported in part by NIH 1R03CA173273