Deep learning-based super-resolution gradient echo imaging of the pancreas: Improvement of image quality and reduction of acquisition time

Magnetic resonance imaging (MRI) of the pancreas is one of the most advanced methods for evaluation of pancreatic parenchyma as well as pancreatic ducts [1]. Despite a rapid development in MR image quality in recent years, there are still challenges due to artifacts caused by physiologic motion in the upper abdomen, especially due to breathing [2]. These artifacts can deteriorate the image clarity and lead to reduction of anatomic detail [3, 4]. This is in particular relevant for dynamic contrast-enhanced (DCE) imaging that is of importance for further diagnostic work-up of pancreatic lesions [1, 5, 6]. Mostly a fast three-dimensional (3D) gradient echo (GRE) sequence (e.g., volumetric interpolated breath-hold examination [VIBE]) is used for non-enhanced as well as enhanced T1-weighted imaging including parallel imaging (PI). PI is the most common acceleration technique to perform imaging within one breath-hold to avoid the occurrence of breathing and motion artifacts. A significant disadvantage of PI is the loss of signal-to-noise ratio (SNR) as well as specific artifacts, which occur in particular at high acceleration factors (> 3–4), limiting the amount of acquisition time (TA) reduction.

A method called iterative denoising has been successfully applied to compensate for acceleration-induced SNR loss [7], [8], [9]. Another technique that has been gaining importance during the last years is called super-resolution showing promising results, especially in combination with deep learning approaches (e.g., in musculoskeletal, brain, and abdominal imaging) [10], [11], [12], [13], [14]. Super-resolution is a method capable of creating images with increased sharpness, SNR, and reduction of blurring and Gibb´s ringing using raw data of conventional acquisitions without the need of change of acquisition parameters leading to a potential improvement of image quality [15, 16]. This approach can also be used in addition to denoising. Furthermore, the combination of super-resolution post-processing including partial Fourier reconstruction settings allows a retrospective simulation of datasets with shorter acquisition time via simulation of more “aggressive” partial Fourier settings (e.g., 6/8 vs. 7/8).

The purpose of this study was to investigate the impact of deep learning-based super-resolution in combination with iterative denoising of T1-weighted VIBE Dixon imaging including simulated TA reduction via more aggressive partial Fourier factors on non-contrast and contrast-enhanced dynamic MRI of the pancreas regarding diagnostic confidence, lesion detectability, and image quality parameters.

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