Computed high-b-value high-resolution DWI improves solid lesion detection in IPMN of the pancreas

Abstract

Objectives: To examine the effect of high-b-value computed diffusion-weighted imaging (cDWI) on solid lesion detection and classification in pancreatic intraductal papillary mucinous neoplasm (IPMN), using endoscopic ultrasound (EUS) and histopathology as a standard of reference.

Methods: Eighty-two patients with known or suspected IPMN were retrospectively enrolled. Computed high-b-value images at b = 1000 s/mm² were calculated from standard (b = 0, 50, 300, and 600 s/mm²) DWI images for conventional full field-of-view (fFOV, 3 × 3 × 4 mm³ voxel size) DWI. A subset of 39 patients received additional high-resolution reduced-field-of-view (rFOV, 2.5 × 2.5 × 3 mm³ voxel size) DWI. In this cohort, rFOV cDWI was compared against fFOV cDWI additionally. Two experienced radiologists evaluated (Likert scale 1-4) image quality (overall image quality, lesion detection and delineation, fluid suppression within the lesion). In addition, quantitative image parameters (apparent signal-to-noise ratio (aSNR), apparent contrast-to-noise ratio (aCNR), contrast ratio (CR)) were assessed. Diagnostic confidence regarding the presence/absence of diffusion-restricted solid nodules was assessed in an additional reader study.

Results: High-b-value cDWI at b = 1000 s/mm² outperformed acquired DWI at b = 600 s/mm² regarding lesion detection, fluid suppression, aCNR, CR, and lesion classification (p = < .001-.002). Comparing cDWI from fFOV and rFOV revealed higher image quality in high-resolution rFOV-DWI compared to conventional fFOV-DWI (p ≤ .001-.018). High-b-value cDWI images were rated non-inferior to directly acquired high-b-value DWI images (p = .095-.655).

Conclusions: High-b-value cDWI may improve the detection and classification of solid lesions in IPMN. Combining high-resolution imaging and high-b-value cDWI may further increase diagnostic precision.

Clinical relevance statement: This study shows the potential of computed high-resolution high-sensitivity diffusion-weighted magnetic resonance imaging for solid lesion detection in pancreatic intraductal papillary mucinous neoplasia (IPMN). The technique may enable early cancer detection in patients under surveillance.

Key points: • Computed high-b-value diffusion-weighted imaging (cDWI) may improve the detection and classification of intraductal papillary mucinous neoplasms (IPMN) of the pancreas. • cDWI calculated from high-resolution imaging increases diagnostic precision compared to cDWI calculated from conventional-resolution imaging. • cDWI has the potential to strengthen the role of MRI for screening and surveillance of IPMN, particularly in view of the rising incidence of IPMNs combined with now more conservative therapeutic approaches.

Keywords: Diffusion magnetic resonance imaging, Pancreas; Pancreatic neoplasms, Pancreatic cysts.

Fig. 1

Image acquisition flow chart

Fig. 2

A mixed-type IPMN in a 75-year-old female patient. The solid tissue component in the pancreatic head (T2w, arrow) is not visible in both conventional and high-resolution DWI at b = 600 s/mm² (B, C) and led to the false diagnosis of a benign IPMN. Also, the conventional high-b-value computed image indicates no clear diffusion restriction (D). However, the high-resolution high-b-value computed image (E) led to the correct diagnosis of malignant IPMN, which was confirmed pathologically after resection. Fluid suppression (dotted arrows) is best achieved in r-cDWI1000. Furthermore, high-resolution high-b-value computed DWI outperforms directly acquired high-resolution high-b-value DWI (F) regarding image quality and fluid suppression

Fig. 3

In an 81-year-old female patient, T2w (A, B) and contrast-enhanced T1w (C) images depict a BD-IPMN in the pancreatic head exhibiting focal contrast enhancement (arrow in C). The mural nodule is clearly better detectable in the high-b-value computed DWI (arrow in E) compared to the standard b-value DWI (arrow in D). Endoscopic ultrasound (F) confirms the presence of a suspicious enhancing mural nodule (arrow). Histopathological analysis after resection confirmed an IPMN with concomitant cancer

Fig. 4

A branch-duct IPMN in the pancreatic body is depicted in the axial T2w image (A). Better fluid suppression within the lesion is seen in the high-b-value computed image (C) compared to the standard b-value DWI (B)

Fig. 5

73-year-old women with a benign IPMN. Malignant IPMN was misdiagnosed based on the standard DWI at b = 600 s/mm² (A) but correctly diagnosed as benign reviewing the computed high-b-value DWI at b = 1000 s/mm.² (B)

Fig. 6

displays the ROC curves for f-aDWI600 (0.54), f-cDWI1000 (0.86), and r-cDWI1000 (0.91)