Thin-slice reverse encoding distortion correction DWI facilitates visualization of non-functioning pituitary neuroendocrine tumor (PitNET)/pituitary adenoma and surrounding normal structures
Authors: Ito Shuichi , Okuchi Sachi , Fushimi Yasutaka , Otani Sayo , Wicaksono Krishna Pandu , Sakata Akihiko , Miyake Kanae Kawai , Numamoto Hitomi , Nakajima Satoshi , Tagawa Hiroshi , Tanji Masahiro , Sano Noritaka , Kondo Hiroki , Imai Rimika , Saga Tsuneo , Fujimoto Koji , Arakawa Yoshiki , Nakamoto Yuji 
Published: March 2024

Abstract
Background
To evaluate the clinical usefulness of thin-slice echo-planar imaging (EPI)-based diffusion-weighted imaging (DWI) with an on-console distortion correction technique, termed reverse encoding distortion correction DWI (RDC-DWI), in patients with non-functioning pituitary neuroendocrine tumor (PitNET)/pituitary adenoma.

Methods
Patients with non-functioning PitNET/pituitary adenoma who underwent 3-T RDC-DWI between December 2021 and September 2022 were retrospectively enrolled. Image quality was compared among RDC-DWI, DWI with correction for distortion induced by B0 inhomogeneity alone (B0-corrected-DWI), and original EPI-based DWI with anterior-posterior phase-encoding direction (AP-DWI). Susceptibility artifact, anatomical visualization of cranial nerves, overall tumor visualization, and visualization of cavernous sinus invasion were assessed qualitatively. Quantitative assessment of geometric distortion was performed by evaluation of anterior and posterior displacement between each DWI and the corresponding three-dimensional T2-weighted imaging. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), and apparent diffusion coefficient values were measured.

Results
Sixty-four patients (age 70.8 ± 9.9 years [mean ± standard deviation]; 33 females) with non-functioning PitNET/pituitary adenoma were evaluated. In terms of susceptibility artifacts in the frontal and temporal lobes, visualization of left trigeminal nerve, overall tumor visualization, and anterior displacement, RDC-DWI performed the best and B0-corrected-DWI performed better than AP-DWI. The right oculomotor and right trigeminal nerves were better visualized by RDC-DWI than by B0-corrected-DWI and AP-DWI. Visualization of cavernous sinus invasion and posterior displacement were better by RDC-DWI and B0-corrected-DWI than by AP-DWI. SNR and CNR were the highest for RDC-DWI.

Conclusions
RDC-DWI achieved excellent image quality regarding susceptibility artifact, geometric distortion, and tumor visualization in patients with non-functioning PitNET/pituitary adenoma.

Relevance statement
RDC-DWI facilitates excellent visualization of the pituitary region and surrounding normal structures, and its on-console distortion correction technique is convenient. RDC-DWI can clearly depict cavernous sinus invasion of PitNET/pituitary adenoma even without contrast medium.

Key points
• RDC-DWI is an EPI-based DWI technique with a novel on-console distortion correction technique.
• RDC-DWI corrects distortion due to B0 field inhomogeneity and eddy current.
• We evaluated the usefulness of thin-slice RDC-DWI in non-functioning PitNET/pituitary adenoma.
• RDC-DWI exhibited excellent visualization in the pituitary region and surrounding structures.
• In addition, the on-console distortion correction of RDC-DWI is clinically convenient.

Graphical Abstract