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Four‐dimensional diffusion‐weighted MR imaging (4D‐DWI): a feasibility study
Author(s) -
Liu Yilin,
Zhong Xiaodong,
Czito Brian G.,
Palta Manisha,
Bashir Mustafa R.,
Dale Brian M.,
Yin FangFang,
Cai Jing
Publication year - 2017
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 - 10.1002/mp.12037
Subject(s) - imaging phantom , magnetic resonance imaging , diffusion mri , multislice , nuclear medicine , effective diffusion coefficient , nuclear magnetic resonance , physics , biomedical engineering , medicine , radiology
Purpose Diffusion‐weighted Magnetic Resonance Imaging (DWI) has been shown to be a powerful tool for cancer detection with high tumor‐to‐tissue contrast. This study aims to investigate the feasibility of developing a four‐dimensional DWI technique (4D‐DWI) for imaging respiratory motion for radiation therapy applications. Materials/Methods Image acquisition was performed by repeatedly imaging a volume of interest (VOI) using an interleaved multislice single‐shot echo‐planar imaging (EPI) 2D‐DWI sequence in the axial plane. Each 2D‐DWI image was acquired with an intermediately low b‐value (b = 500 s/mm 2 ) and with diffusion‐encoding gradients in x, y, and z diffusion directions. Respiratory motion was simultaneously recorded using a respiratory bellow, and the synchronized respiratory signal was used to retrospectively sort the 2D images to generate 4D‐DWI. Cine MRI using steady‐state free precession was also acquired as a motion reference. As a preliminary feasibility study, this technique was implemented on a 4D digital human phantom (XCAT) with a simulated pancreas tumor. The respiratory motion of the phantom was controlled by regular sinusoidal motion profile. 4D‐DWI tumor motion trajectories were extracted and compared with the input breathing curve. The mean absolute amplitude differences (D) were calculated in superior–inferior (SI) direction and anterior–posterior (AP) direction. The technique was then evaluated on two healthy volunteers. Finally, the effects of 4D‐DWI on apparent diffusion coefficient (ADC) measurements were investigated for hypothetical heterogeneous tumors via simulations. Results Tumor trajectories extracted from XCAT 4D‐DWI were consistent with the input signal: the average D value was 1.9 mm (SI) and 0.4 mm (AP). The average D value was 2.6 mm (SI) and 1.7 mm (AP) for the two healthy volunteers. Conclusion A 4D‐DWI technique has been developed and evaluated on digital phantom and human subjects. 4D‐DWI can lead to more accurate respiratory motion measurement. This has a great potential to improve the visualization and delineation of cancer tumors for radiotherapy.