Characterization of B0-field fluctuations in prostate MRI. (2nd November 2020)

• Record Type: Journal Article
• Authors: Shrestha Kakkar, Lebina; Usman, Muhammad; Arridge, Simon; Kirkham, Alex; Atkinson, David
• Is Part Of: Physics in medicine & biology. Volume 65:Number 21(2020:Nov.)
• Publication Date: 2020-11-02
• Subjects: B0-field -- prostate MRI -- diffusion MRI -- mpMRI -- prostate phantom -- CEST -- MRS; Biophysics -- Periodicals; Medical physics -- Periodicals; 610.153
• DOI: 10.1088/1361-6560/abbc7f
• Languages: English
• ISSNs: 0031-9155

Abstract

Abstract: Multi-parametric MRI is increasingly used for prostate cancer detection. Improving information from current sequences, such as T2-weighted and diffusion-weighted (DW) imaging, and additional sequences, such as magnetic resonance spectroscopy (MRS) and chemical exchange saturation transfer (CEST), may enhance the performance of multi-parametric MRI. The majority of these techniques are sensitive to B0 -field variations and may result in image distortions including signal pile-up and stretching (echo planar imaging (EPI) based DW-MRI) or unwanted shifts in the frequency spectrum (CEST and MRS). Our aim is to temporally and spatially characterize B0 -field changes in the prostate. Ten male patients are imaged using dual-echo gradient echo sequences with varying repetitions on a 3 T scanner to evaluate the temporal B0 -field changes within the prostate. A phantom is also imaged to consider no physiological motion. The spatial B0 -field variations in the prostate are reported as B0 -field values (Hz), their spatial gradients (Hz/mm) and the resultant distortions in EPI based DW-MRI images ( b -value = 0 s/mm 2 and two oppositely phase encoded directions). Over a period of minutes, temporal changes in B0 -field values were ≤19 Hz for minimal bowel motion and ≥30 Hz for large motion. Spatially across the prostate, the B0 -field values had an interquartile range of ≤18 Hz (minimal motion) and ≤44 Hz (large motion). The B0 -field gradients were between −2 and 5 Hz/mm (minimal motion) and 2 and 12 Hz/mm (large motion). Overall, B0 -field variations can affect DW, MRS and CEST imaging of the prostate.