Diffusion-weighted imaging in the differential diagnosis of cystic lesions of the pancreas.

Objective: The purpose of our study was to evaluate the value of diffusion-weighted imaging (DWI) in the differential diagnosis of pancreatic cysts.

Subjects And Methods: Forty-two cysts (16 simple cysts, seven pseudocysts, five abscesses, three hydatid cysts, two serous cystadenomas, three mucinous cystadenomas, two mucinous cystadenocarcinomas, four cystic degenerated adenocarcinomas) were included in this prospective study. Single-shot spin-echo echo-planar DWI was performed with three b factors (0, 500, and 1,000 s/mm(2)), and apparent diffusion coefficients (ADCs) were calculated. On DWI, the signal intensity of the cysts was visually compared with the signal intensity of the pancreas parenchyma. For the quantitative evaluation, cyst-to-pancreas signal intensity ratios, ADC of the lesions, and cyst-to-pancreas ADC ratios were compared.

Results: On visual evaluation, all cystic lesions were hyperintense on DWI with b factors of 0 and 500 s/mm(2). On DWI with a b factor of 1,000 s/mm(2), all abscesses and hydatid and neoplastic cysts were hyperintense, whereas most of the simple and pseudocysts were isointense. Quantitatively, with b factors of 0 and 500 s/mm(2), no statistical significance was achieved. With a b factor of 1,000 s/mm(2), the cyst-to-pancreas signal intensity ratios of the abscesses and hydatid and neoplastic cysts were significantly higher than those of the simple cysts and pseudocysts. Setting the cutoff value of signal intensity ratio at 1.9, the cyst-to-pancreas signal intensity ratio had a sensitivity of 70% and a specificity of 90% for differentiating abscesses, hydatid cysts, and neoplastic cysts from simple cysts and pseudocysts. The ADC and the ADC ratios of the abscesses, hydatid cysts, and neoplastic cysts were significantly lower than those of the simple cysts and pseudocysts.

Conclusion: DWI may help in the differential diagnosis of pancreatic cysts.