Apparent diffusion coefficient measurements of the pancreas, pancreas carcinoma, and mass-forming focal pancreatitis

Abstract

Background: Mass-forming focal pancreatitis (FP) may mimic pancreatic cancer (PC) on magnetic resonance (MR) imaging, and the preoperative differential diagnosis is often difficult. Recently, the usefulness of diffusion-weighted imaging (DWI) in the diagnosis of pancreatic cancer has been reported in several studies. Purpose: To investigate if apparent diffusion coefficient (ADC) measurements based on diffusion-weighted echo-planar imaging (DW-EPI) may distinguish between normal pancreas parenchyma, mass-forming focal pancreatitis, and pancreas carcinoma. Material and Methods: MRI was performed on 64 patients: 24 with pancreas carcinoma (PC), 20 with massforming focal pancreatitis (FP), three patients with other focal pancreatic disease as well as 17 controls without any known pancreatic disease. Diffusion-weighted sequence with ADC maps and T2-weighted sequence for anatomical information was performed. Apparent diffusion coefficient (ADC) maps were automatically created and analyzed using a dedicated user interface. In the group with pancreas disease the abnormal parenchyma was detected by using T1-and T2-weighted images and the region of interest (ROI) was transferred exactly to the ADC map and the coefficients were registered. In the control group the ROI was set to the head of the pancreas followed by a similar registration of the ADCs. Results: ADC values for mass-forming FP and PC differed significantly from ADC values for normal pancreas parenchyma (P ¼ 0.001/P ¼ 0.002). Mean ADC values for mass-forming FP were 0.69 + 0.18 Â 10 23 mm 2 /s.

The Role of Diffusion Weighted MR Imaging in the Diagnosis of Acute Pancreatitis

“…Thomas et al (Thomas et al, 2012) presented 93% sensitivity and 87% specificity in the detection of AP with b values 0 and 800 sec/mm2, predicted lower ADC values in the AP group than the normal controls. Wiggermann et al (Wiggermann et al, 2012) revealed significant differences for ADC values between pancreatic cancer and normal pancreas, between focal pancreatitis and normal parenchyma which can clearly differentiate the normal pancreatic tissue and abnormal pancreas parenchyma, without any statistical differences between pancreatic cancer and pancreatitis in a series of 64 patients. The consequent obstacle of a significant overlap of ADC values for pancreatic cancer and chronic pancreatitis can be due to fibrotic and focal inflammatory reactions in chronic pancreatitis, causing difficulty in the differentiation of both of these pancreatic lesions (Takeuchi et al, 2008;Wiggermann et al, 2012;Taniguchi et al, 2009).…”

“…Wiggermann et al (Wiggermann et al, 2012) revealed significant differences for ADC values between pancreatic cancer and normal pancreas, between focal pancreatitis and normal parenchyma which can clearly differentiate the normal pancreatic tissue and abnormal pancreas parenchyma, without any statistical differences between pancreatic cancer and pancreatitis in a series of 64 patients. The consequent obstacle of a significant overlap of ADC values for pancreatic cancer and chronic pancreatitis can be due to fibrotic and focal inflammatory reactions in chronic pancreatitis, causing difficulty in the differentiation of both of these pancreatic lesions (Takeuchi et al, 2008;Wiggermann et al, 2012;Taniguchi et al, 2009). Head and body of pancreas reveal slightly higher ADC values when compared with the tail, ADC values of pancreatic adenocarcinoma tend to be lower than normal pancreas b factor images can't be totally attributed to the T2-shine-through effect (Wang et al, 2011;Takeuchi et al, 2008;Wiggermann et al, 2012;Inan et al, 2008).…”

“…Conventional Pancreatic MR imaging has limitations in differentiating acute from chronic pancreatitis and signal changes in some mild forms of AP (Thomas et al, 2012;Sica et al, 2002). Besides depicting cystic and solid neoplasms of pancreas, DWI has become recently applied in imaging of acute and chronic inflammation of the pancreas, regarding increased signal at DWI and decreased ADC values (Thomas et al, 2012;Shinya et al, 2009;Balci et al, 2009;Takeuchi et al, 2008;Wiggermann et al, 2012) (Figures 1 and 2). Acute inflammation causes increased vascular permeability and edema, fluid accumulation in the affected area which lead to increased diffusion and ADC values with some variations and exceptions, if fibrosis exists with acute inflammation, restricted diffusion and lower ADC values are quantified, Diffusionweighted images-with different b-values, ADC map and the calculated ADC value is really important for the diagnosis of acute and/or chronic inflammatory diseases, the perfusion value, however which can also be calculated DWI and ADC maps, is also different in the acute and chronic form of pancreatitis that can aid in the diagnosis and depiction of inflammatory pancreatic disorders ( Figure 3a and b) (Shinya et al, 2008;Balci et al, 2009;Inan et al, 2008).…”

“…The consequent obstacle of a significant overlap of ADC values for pancreatic cancer and chronic pancreatitis can be due to fibrotic and focal inflammatory reactions in chronic pancreatitis, causing difficulty in the differentiation of both of these pancreatic lesions (Takeuchi et al, 2008;Wiggermann et al, 2012;Taniguchi et al, 2009). Head and body of pancreas reveal slightly higher ADC values when compared with the tail, ADC values of pancreatic adenocarcinoma tend to be lower than normal pancreas b factor images can't be totally attributed to the T2-shine-through effect (Wang et al, 2011;Takeuchi et al, 2008;Wiggermann et al, 2012;Inan et al, 2008). T2-shine-effect exhibit high signal both in DWI and ADC maps, may be mistaken for restricted diffusion and as DWI has significant T2-weighting because of long TE, this effect can be overcome by use of short TE and high b-value, but can't be avoided easily in DWI Le Bihan et al, 1988;Koh et al, 2006).…”

“…Standard application of DWI is based on quantitative approach and limited scanning time acquired by breath-holding, motion artefacts does not permit thin-slice DW parenchyma due to dense fibrosis and increased cellular elements, whereas higher or lower ADC values than the normal appearing pancreas exist in AP, due to the nature of inflammation in the gland Wiggermann et al, 2012;Fattahi et al, 2009;Momtahen et al, 2008). Acute relapsing pancreatitis in the setting form of chronic pancreatitis show increased ADC values, predominant loose fibrosis, replacement of normal parenchyma with edematous fibrosis and or reduced exocrine function which reduces the diffusion of water in tissues, result in decreased ADC values Wiggermann et al, 2012;Bockman et al, 1986) (Figure 3c). …”