Deep learning-based magnetic resonance imaging reconstruction for improving the image quality of reduced-field-of-view diffusion-weighted imaging of the pancreas

Figure 2 A 45-year-old male with an unspecified pancreas cyst. Reduced-field-of-view diffusion-weighted image [field-of-view optimized and constrained undistorted single-shot (FOCUS)] with b-values of 0 and 600 s/mm², and apparent diffusion coefficient (ADC) maps of FOCUS-deep learning-based reconstruction (DLR)+ (A-C), FOCUS-DLR− (D-F), and conventional FOCUS (FOCUS-conv) (G-I). FOCUS-DLR+ provides reduced image noise and better contrast ratio between the pancreas parenchyma and adjacent fat tissue [contrast ratios (CR)_pancreas-fat] compared to FOCUS-DLR- and FOCUS-conv. Both FOCUS-DLR+ and FOCUS-DLR- show better image-quality scores for sharpness of pancreas contour, CR_pancreas-fat, and contrast ratio between the pancreas cystic lesion and pancreas parenchyma (CR_{lesion-pancreas}) compared to FOCUS-conv. FOCUS-DLR- provides a better CR_{lesion-pancreas} than FOCUS-DLR+, but there is no difference in the image-quality score for visualization of the cystic lesion of the pancreas between FOCUS-DLR+ and FOCUS-DLR-. The average image-quality scores from two radiologists for FOCUS-DLR+, FOCUS-DLR- and FOCUS-conv are as follows: Sharpness of the pancreas contour, 3.5, 3.0, and 2.0; image noise, 3.5, 2.5, and 2.0; and visualization of pancreatic cystic lesion, 3.0, 2.5, 1.0, respectively. The average CR_pancreas-fat and CR_{lesion-pancreas} on FOCUS with a b-value of 600 s/mm² from two radiologists for FOCUS-DLR+, FOCUS-DLR- and FOCUS-conv are 0.54 and 0.75, 0.38 and 0.81, and 0.23 and 0.10, respectively. The average ADCs of the pancreatic parenchyma and pancreatic cystic lesion of two radiologists for FOCUS-DLR+, FOCUS-DLR- and FOCUS-conv are 1.59 and 2.28, 1.49 and 2.26, and 1.93 and 4.01 (× 10^-3 mm²/s), respectively.