Acute pancreatitis successfully diagnosed by diffusion-weighted imaging: A case report

Magnetic resonance imaging in the evaluation and management of acute pancreatitis: a review of current practices and future directions

Acute pancreatitis is a condition marked by inflammation of the pancreas and surrounding tissues. While the majority of cases of acute pancreatitis are mild, a minority of severe cases are the primary contributors to the morbidity and mortality attributed to this condition. Retroperitoneal morphologic changes can be detected by utilization of various imaging modalities, and their accurate evaluation is crucial for effective management. Acute pancreatitis is commonly diagnosed using computed tomography (CT). However, there are certain clinical scenarios where magnetic resonance imaging (MRI) may have superiority over CT. In particular, MRI is useful in cases where patients cannot receive iodinated CT contrast, or where there is a need to investigate the underlying cause of acute pancreatitis. Additionally, MRI can be utilized to evaluate ductal disconnection and guide interventions for necrotic collections. The unique features of MRI can be particularly useful, including its ability to provide superior contrast resolution and to offer greater functional information through techniques such as diffusion-weighted imaging. The aim of this review is to discuss the MRI assessment of individuals with acute pancreatitis. Additionally, the recent advances in MRI for evaluation of acute pancreatitis will also be introduced.

Diagnosis of Acute Pancreatitis Using Postmortem Computed Tomography and Postmortem Magnetic Resonance Imaging: A Case Report and a Review of Literature

ABSTRACT

Acute pancreatitis (AP) is inflammation of the pancreas, which may be due to a wide variety of etiologies that share a final common pathway of premature activation of pancreatic enzymes and resultant autodigestion of pancreatic parenchyma. Acute pancreatitis is easy to diagnose clinically, with the presence of at least 2 of the 3 criteria (upper abdominal pain, serum amylase or lipase level greater than 3 times the upper limit of normal, or characteristic findings on imaging studies) of the revised Atlanta classification. However, postmortem imaging examinations of pancreatitis are extremely rare, and very few successful cases have been reported. Here, we present a case report of a single patient who underwent autopsy and postmortem imaging. Postmortem computed tomography (PMCT) and postmortem magnetic resonance imaging (PMMRI) showed peripancreatic inflammation and acute peripancreatic fluid collection in the left anterior pararenal space, which is consistent with the examination by autopsy. The advantages of PMMRI in AP have also been demonstrated. Our study also confirmed the advantage of PMCT angiography in the diagnosis of AP. To the best of our knowledge, this is the first report of PMCT and PMMRI combined with postmortem pathology in the diagnosis of AP.

Acute pancreatitis: Structured report template of magnetic resonance imaging

Acute pancreatitis (AP) is a common acute abdomen disease of the digestive system. It has a potentially fatal risk because of its variable severity and various complications. With the widespread application of the Revised Atlanta Classification, new requirements for AP imaging reports are introduced. Experts in abdominal radiology and pancreatology in the United States published the first structured computed tomography reporting template for AP in 2020. However, there is no corresponding structured magnetic resonance imaging (MRI) reporting template globally. Therefore, this article focuses on the structured MRI report of AP images from our pancreatitis imaging center, which is intended to improve the systematic understanding of this disease and standardize the writing of MRI structured reports. In the meantime, we aim to promote the clinical diagnosis and assessment of MRI efficacy for AP and its multiple complications. It is further intended to facilitate academic exchanges and scientific research between different medical centers.

Optimizing b-values for accurate depiction of pancreatic cancer with tumor-associated pancreatitis on computed diffusion-weighted imaging

PURPOSE

To determine the optimal b-value for accurate depiction of pancreatic cancer (PC) in patients with active tumor-associated pancreatitis (TAP), using computed diffusion-weighted imaging (cDWI) with a range of b-values up to 3000 s/mm².

METHODS

The study protocol was approved by the institutional review board. We retrospectively analyzed 34 consecutive PC cases with active TAP who underwent pancreatectomy without preoperative therapy. Four cDWI datasets with b-values of 1500-3000 s/mm² (cDWI₁₅₀₀-cDWI₃₀₀₀) were generated from the original DWI datasets with b-values of 0 and 1000 s/mm² obtained using a 3-T scanner. Two board-certified radiologists evaluated images qualitatively (tumor conspicuity and total image quality), and another two board-certified radiologists placed regions of interest for quantitative evaluations (apparent diffusion coefficient [ADC] values of both lesions, contrast ratio [CR] of PC to active TAP, and volume ratio [VR] of PC to surgical specimen).

RESULTS

As the b-value increased, tumor conspicuity improved significantly in cDWI₂₀₀₀ and cDWI₂₅₀₀ (P = 0.0121 and 0.0015, respectively), although total image quality decreased in all cDWIs compared with DWI₁₀₀₀ (P < 0.0001). Significantly lower ADC values were seen in PC (P < 0.0001). All cDWI groups showed positive correlation between the tumor conspicuity and ADC difference between PC and TAP. CR increased with the b-value, while VR decreased. Significant equivalence of VR to the surgical specimen was seen on cDWI₂₀₀₀ (P = 0.0031).

CONCLUSION

Accurate depiction of PC was optimal with cDWI₂₀₀₀ in the presence of active TAP.

Utility of diffusion weighted imaging with the quantitative apparent diffusion coefficient in diagnosing residual or recurrent hepatocellular carcinoma after transarterial chemoembolization: a meta-analysis

Background

Accurate and early diagnosis of residual tumors or intrahepatic recurrences after TACE is critically needed for determining the success of treatments and for guiding subsequent therapeutic planning. This meta-analysis was performed to assess the efficacy of diffusion weighted imaging (DWI) with the quantitative apparent diffusion coefficient (ADC) value in diagnosing residual or recurrent hepatocellular carcinoma after transarterial chemoembolization (TACE).

Materials and methods

A comprehensive literature search of PubMed, Embase, Web of Science, Scopus and the Cochrane Library database, from inception to July 2019, was conducted to select original studies on diagnosing residual or recurrent HCCs after TACE using DWI sequence with its ADC value. Two researchers independently chose study, extracted data, conducted meta-analysis, and evaluated methodological quality according to Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool.

Results

Twelve studies comprising 624 patients and 712 tumors were finally included. The pooled sensitivity, specificity and AUC value of DWI in diagnosing residual or recurrent HCCs after TACE were 85% (95%CI: 74–92%), 83% (95%CI: 75–88%) and 0.90 (95%CI: 0.87–0.92), respectively. Residual or recurrent HCCs have significantly lower ADC value than necrotic tumors (MD = -0.48, 95%CI: − 0.69~ − 0.27, P < 0.01).

Conclusion

This study demonstrated that DWI performed better in diagnosing residual or recurrent HCCs after TACE, and ADC value may serve as alternatives for further evaluation of residual or recurrent leisions in HCC patients after TACE.

Assessment of acute obstructive pancreatitis by magnetic resonance imaging: Predicting the occurrence of pancreatic fistula following pancreatoduodenectomy

The aim of the present study was to assess the effect of preoperative acute obstructive pancreatitis on the risk of the occurrence of pancreatic fistula (PF) following pancreaticoduodenectomy. A total of 22 patients who developed postoperative PF were carefully matched with 22 control patients without PF according to demographic data, pancreatic pathology, presenting symptoms and other surgery-associated parameters. These parameters were compared between these two groups. The mean pancreatic apparent diffusion coefficient (ADC) values in the fistula group were 1.14±0.31×10^-3 mm²/s, which was significantly decreased compared with the non-fistula group (1.48±0.44×10^-3 mm²/s) (P=0.005). The pancreas-muscle signal intensity (SI) ratio on fat-suppressed T1 weighted image (rT1) in the fistula group was 1.71±0.25, which was significantly increased compared with the non-fistula group (1.25±0.29) (P<0.001). The pancreas-muscle SI ratios on fat-suppressed T2 weighted image (T2WI) in the fistula group and the non-fistula group were 0.72±0.08 and 0.62±0.07, respectively (P=0.79). There was no significant difference in pancreas-muscle SI ratio on fat-suppressed T2-weighted image (rT2) value between these two groups. Based on the receiver operating characteristic curve, the optimal cut-off value of ADC as a criterion for prediction of pancreatic fistula was 1.29×10^-3 mm²/s, which yielded a sensitivity of 77.3% and a specificity of 63.6%. In conclusion, the severity of acute obstructive pancreatitis was negatively associated with ADC values and pancreas-muscle SI ratio on rT1 images, which may be useful for predicting the occurrence of PF preoperatively.

Diffusion-weighted imaging in hemorrhagic abdominal and pelvic lesions: restricted diffusion can mimic malignancy

Diffusion-weighted imaging (DWI) is an increasingly utilized sequence in the assessment of abdominal and pelvic lesions. Benign lesions containing hemorrhagic products, with conglomerates of tightly packed blood cells or fibers, can have restricted water diffusion on DWI and apparent diffusion coefficient maps. Such lesions can have restricted diffusion erroneously attributed to malignancy. This review illustrates benign hemorrhagic lesions displaying restricted diffusion, with histopathologic correlation in relevant cases.

Errors in imaging the pregnant patient with acute abdomen

Pregnant women with an acute abdomen present a critical issue due to the necessity for an immediate diagnosis and treatment; in fact, a diagnostic delay could worsen the outcome for both the mother and the fetus. There is evidence that emergencies during pregnancy are subject to mismanagement; however, the percentage of errors in the diagnosis of emergencies in pregnancy has not been studied in depth. The purpose of this article is to review the most common imaging error emergencies. The topics covered are divided into gynecological and non-gynecological entities and, for each pathology, possible errors have been dealt with in the diagnostic pathway, the possible technical errors in the exam execution, and finally the possible errors in the interpretation of the images. These last two entities are often connected owing to a substandard examination, which can cause errors in the interpretation. Consequently, the systemization of errors reduces the possibility of reoccurrences in the future by providing a valid approach in helping to learn from these errors.

Magnetic resonance imaging of retroperitoneal interfascial plane involvement in acute pancreatitis

BACKGROUND

To study the magnetic resonance imaging (MRI) features of acute pancreatitis (AP) involving the retroperitoneal interfascial planes and to analyze the correlations of interfascial plane involvement with the magnetic resonance severity index (MRSI) and the Acute Physiology and Chronic Health Evaluation (APACHE II) scoring system.

METHODS

A total of 316 consecutive patients with AP between November 2011 and August 2013 were retrospectively analyzed. The extension and path of the inflammation spreading along the retroperitoneal interfascial plane on MRI were graded from grade 0 to grade 5. The relationships between interfascial plane involvement and MRSI and APACHE II were analyzed.

RESULTS

Of the 316 patients with AP, 293 patients (92.7%) had interfascial plane involvement, which appeared as interfascial plane edema, thickening and effusion. There were 60, 105, 78, 25, and 25 patients in grades 1, 2, 3, 4, and 5, respectively. Interfascial plane involvement strongly correlated with the MRSI score (r=0.703), but was only weakly correlated with the APACHE-II score (r=0.291).

CONCLUSIONS

MRI depicts the characteristics of interfascial plane involvement in AP. The value of interfascial plane involvement for determining the disease severity is likely to be limited.

Diffusion-weighted magnetic resonance imaging for non-neoplastic conditions in the hepatobiliary and pancreatic regions: pearls and potential pitfalls in imaging interpretation

Potentially, diffusion-weighted magnetic resonance imaging (DWI) can assess the functional information on concerning the status of tissue cellularity, because increased cellularity is associated with impeded diffusion. DWI in the hepatobiliary and pancreatic regions has demonstrated the usefulness to detect malignant lesions and differentiate them from benign lesions. However, it has been shown more recently that there is some overlap in ADC values for benign and malignant neoplasms. Moreover, some non-neoplastic lesions in the hepatobiliary and pancreatic regions exhibit restricted diffusion on DWI, because of pus, inflammation, or high cellularity. Focal eosinophilic liver disease, hepatic inflammatory myofibroblastic tumor, granulomatous liver disease, acute cholecystitis, xanthogranulomatous cholecystitis, focal pancreatitis, or autoimmune pancreatitis frequently exhibit restricted diffusion on DWI, which may be confused with malignancy in the hepatobiliary and pancreatic regions. Thus, DWI should not be interpreted in isolation, but in conjunction with other conventional images, to avoid the diagnostic pitfalls of DWI. Nevertheless, the presence of diffusion restriction in the non-neoplastic lesions sometimes provides additional information regarding the diagnosis, in problematic patients where conventional images have yielded equivocal findings. DWI may help differentiate hepatic abscess from malignant necrotic tumors, gallbladder empyema from dense bile or sludge in the gallbladder, and pylephlebitis from bland thrombosis in the portal vein. Therefore, knowledge of DWI findings to conventional imaging findings of diffusion-restricted non-neoplastic conditions in the hepatobiliary and pancreatic regions helps establishing a correct diagnosis.

Correlation between apparent diffusion coefficients on diffusion-weighted MRI and standardized uptake value on FDG-PET/CT in pancreatic adenocarcinoma

BACKGROUND

Diffusion-weighted magnetic resonance imaging (DW-MRI) and 2-deoxy-2-[18F]fluoro-D-glucose-positron emission tomography/computed tomography (PET/CT) is increasingly recognized as important for assessing tumor malignancy in oncology. Apparent diffusion coefficient (ADC) and standardized uptake value (SUV) are negatively correlated in some types of cancer based on tumor aggressiveness.

PURPOSE

To evaluate relationships between ADC of magnetic resonance imaging and SUV of PET/CT in pancreatic adenocarcinomas.

MATERIAL AND METHODS

Twenty-nine patients histopathologically diagnosed with pancreatic adenocarcinomas were evaluated. ADC maps were generated from 3 T-MRI using b values (b = 0, 800 s/mm(2)). PET/CT was performed 60 min after intravenous injection of FDG (3.7 MBq/kg). The margins of tumors on DW-MRI and PET/CT were assessed to measure ADC and SUV of tumor appropriately. For tumors considered well-marginated, minimal and mean ADC as well as maximal and mean SUV were measured. The correlation of ADC and SUV were statistically evaluated and survival period stratified on ADC and SUV also evaluated.

RESULTS

Twenty-two tumors on DW-MRI and 25 on PET/CT were deemed well-marginated. Minimal ADC was significantly and negatively correlated with maximal and mean SUV (r = -0.61, P = 0.0040; r = -0.66, P = 0.0015), and mean ADC also showed significantly and negatively correlation with maximal and mean SUV (r = -0.50, P = 0.024; r = -0.54, P = 0.012). There was no significant difference on overall survival stratified on ADC and SUV.

CONCLUSION

ADC and SUV were significantly correlated in pancreatic adenocarcinomas, although no significant findings were observed in overall survival.

Diagnosis of acute pancreatitis by diffusion-weighted magnetic resonance imaging

Diffusion-weighted magnetic resonance imaging has emerged as a successful technique in the early diagnosis of acute pancreatitis. An 82-year-old male patient suspected of acute pancreatitis refused to undergo intravenous contrast-enhanced abdominal computed tomography due to a history of previous allergic reactions to contrast medium. He was imaged with diffusion-weighted magnetic resonance imaging without the use of oral or intravenous contrast material. Diffuse hyperintensity in the pancreas with a relevant apparent diffusion coefficient map showing diffuse hypointensity was demonstrated. The findings were interpreted as restricted diffusion and were diagnostic for acute pancreatitis. Diffusion-weighted magnetic resonance imaging, an imaging modality that does not involve ionizing radiation and does not require the use of contrast material, can successfully demonstrate the manifestations of acute pancreatitis.

Value of diffusion-weighted MRI for differentiating malignant from benign intraductal papillary mucinous neoplasms of the pancreas

OBJECTIVE

The purpose of this study was to evaluate whether the use of diffusion-weighted MRI (DWI) increases diagnostic accuracy in the differentiation of malignant from benign intraductal papillary mucinous neoplasms (IPMNs) of the pancreas over the accuracy of contrast-enhanced MRI with MRCP.

MATERIALS AND METHODS

A total of 61 patients with surgically resected IPMNs (19 malignant, 42 benign) who underwent gadoxetic acid-enhanced MRI, DWI, and MRCP were included. Two blinded observers evaluated two image sets, that is, conventional MRI with MRCP images versus combined conventional MRI with MRCP and DW images, and scored their confidence for malignancy of IPMNs. Qualitative analyses of the IPMNs were also conducted. Diagnostic performance (ROC curve analysis), accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were evaluated. The Fisher exact test was used to compare groups.

RESULTS

The diagnostic performance (area under the ROC curve [Az]) with respect to predicting malignancy of IPMNs improved significantly for both observers after additional review of DW images (p < 0.05). The diagnostic accuracy, sensitivity, specificity, PPV, and NPV of combined conventional and DW images were higher than those of conventional MR images alone. Diffusion restriction was more often present in malignant IPMNs (78.9%) than in benign IPMNs (16.7%) (p < 0.001) with excellent interobserver agreement (ĸ = 0.965).

CONCLUSION

Compared with conventional MRI alone, adding DWI to conventional MRI improves diagnostic accuracy with increased specificity for differentiating malignant from benign IPMNs of the pancreas.

Diffusion-weighted magnetic resonance imaging indicates the severity of acute pancreatitis

PURPOSE

To test the use of diffusion-weighted magnetic resonance imaging (DW-MRI) to differentiate between different degrees of severity of acute pancreatitis (AP).

METHOD

Thirty-six patients who underwent DW-MRI and magnetic resonance cholangiopancreatography were divided into patients with mild AP (mAP, n = 15), patients with necrotizing AP (nAP, n = 8), and patients with a normal pancreas (nP, n = 15; controls). The pancreas was divided into head, body, and tail, and each segment was classified according to image features: pattern 1, normal; pattern 2, mild inflammation; and pattern 3, necrosis. Apparent diffusion coefficients (ADCs) were measured in each segment and correlated with clinical diagnoses.

RESULTS

A total of 108 segments was assessed (three segments per patient). Segments classified as pattern 1 in the nP and mAP groups showed similar ADC values (P = 0.29). ADC values calculated for the pancreatic segments grouped according to the different image patterns (1-3) were significantly different (P < 0.001). Comparisons revealed significant differences in signal intensity between all three patterns (P < 0.05).

CONCLUSIONS

DW-MRI was a compatible and safe image option to differentiate tissue image patterns in patients with mAP, nAP, and nP, mainly in those with contraindications to contrast-enhanced MRI (which is classically required for determining the presence of necrosis) or computed tomography. ADC measures allowed precise differentiation between patterns 1, 2, and 3.

Magnetic resonance imaging for the normal mesostenium and involvement of the mesostenium in acute pancreatitis

The main point of this paper is to study MRI findings of the normal mesostenium and the involvement of the mesostenium in acute pancreatitis and to discuss the relationship between the involvement of the mesostenium and the severity of acute pancreatitis. In clinical practice, the mesenterical involvement in acute pancreatitis was often observed on MRI in daily works, which was little recorded in the reported studies. We conducted the current study to assess the mesenterical involvement in acute pancreatitis with MRI. We found that the mesenterical involvement of acute pancreatitis patients is common on MRI. The mesenterical involvement has a positive correlation with the MR severity index and the Acute Physiology and Chronic Healthy Evaluation II scoring system. It has been shown that MR can be used to visualize mesenterical involvement, which is a supplementary indicator in evaluating the severity of acute pancreatitis and local and systemic complications.

[Case of inflammatory lesion in urinary bladder showing high signal intensity on diffusion-weighted MRI: correlation with histopathological finding]

A 66-year-old woman was referred to our department for thickening bladder wall incidentally found during postoperative follow-up of transverse colon cancer. Cystoscopy showed edematous tumor with a diameter of 5 cm on the right wall. Deep portion of the tumor showed high intensity on diffusion-weighted magnetic resonance imaging (DW-MRI). Transurethral resection and transvaginal needle biopsy was performed, and pathological examination revealed granulation tissues mainly consisted of inflammatory cells and fibrosis. DW-MRI is a functional imaging constructed by quantifying the diffusion of water molecules. Recently, the feasibility of this imaging in the diagnosis of bladder cancer has been reported. However, we should keep in mind that granulation tissues consisted of inflammatory cells and fibrosis is also possible to be positive for DW-MRI.

Diffusion MRI of acute pancreatitis and comparison with normal individuals using ADC values

The aim of this study was to retrospectively measure and compare pancreatic apparent diffusion coefficient (ADC) in patients with acute pancreatitis (AP) with aged matched controls who underwent diffusion weighted imaging (DWI). The institutional review board approved this retrospective Health Insurance Portability and Accountability Act compliant study with a waiver for informed consent. Pancreatic ADC values from 27 patients with a clinical diagnosis of AP and 38 normal age-matched controls evaluated with DWI (b = 0 and 800 mm(2)/s) were retrospectively and independently measured by two radiologists. The ADCs were compared between the groups and between each of the pancreatic segments in the normal group. Inter-observer reliability was calculated and receiver operating characteristic analysis was used to determine the sensitivity and specificity of DW imaging in the diagnosis of acute pancreatitis. P < 0.05 was considered statistically significant. The ICC for inter-observer reliability was 0.98 in the control and 0.97 in the AP group. The mean pancreatic ADC in the AP group (1.32 × 10(-3) mm(2)/s ± 0.13) was significantly lower than in the normal group (1.77 × 10(-3) mm(2)/s ± 0.32). There was no significant difference in mean ADCs between each of the pancreatic segments in the controls. A threshold ADC value of 1.62 × 10-3 mm(2)/s yielded a sensitivity of 93% and specificity of 87% for detecting acute pancreatitis for b values of 0 and 800 s/mm(2). Pancreatic ADCs are significantly lower in patients with AP than normal controls.

Pitfalls in abdominal diffusion-weighted imaging: how predictive is restricted water diffusion for malignancy

OBJECTIVE

As diffusion-weighted imaging is increasingly implemented into routine protocols of abdominal MRI, abnormal findings in expected and unexpected locations become more common. The aim of our retrospective study was to investigate the specificity of restricted diffusion in differentiation of benign from malignant abdominal disease.

MATERIALS AND METHODS

Two hundred thirty consecutively registered patients underwent abdominal MRI including diffusion-weighted imaging (single-shot spin-echo echo-planar sequence) with b values of 0, 150, 500, and 1,000 s/mm(2). Lesions were detected by two blinded readers using only the images with a b value of 1,000 s/mm(2), and representative apparent diffusion coefficients were measured. Lymph nodes were not documented.

RESULTS

Fifty-two of the 230 patients had a total of 55 lesions with restricted diffusion (23.9%). The mean apparent diffusion coefficient was 809 mm(2)/s. Forty-three lesions (78.2%) were malignant. The 12 benign lesions were liver hemangioma, liver adenoma, autoimmune pancreatitis, pancreatic teratoma, two abscesses, three cases of inflammatory bowel wall thickening due to Crohn's disease, Bartholin cyst, hemorrhagic ovarian cyst, and renal Rosai-Dorfman disease.

CONCLUSION

Restricted diffusion is generally considered to be associated with malignant tumors because of the high cellularity of these tumors. However, in interpretation of diffusion-weighted images, it should be kept in mind that a number of benign lesions, as many as 22% in our cohort, can exhibit restricted diffusion on images with high b values, thus mimicking malignant lesions.

Added value of diffusion-weighted imaging in the MRI assessment of perilesional tumor recurrence after chemoembolization of hepatocellular carcinomas

PURPOSE

To investigate the additional value of diffusion-weighted imaging (DWI) in the MRI assessment of perilesionally recurrent hepatocellular carcinomas (HCCs) after transcatheter arterial chemoembolization (TACE).

MATERIALS AND METHODS

For gadopentetate dimeglumine-enhanced multiphasic dynamic images with precontrast T1- and T2-weighted images of 23 patients treated with TACE, two radiologists independently sorted the confidence levels for the presence of a viable tumor in the vicinity of the treated lesions into five grades. In another session, images from DWI (b factor = 50, 400, and 800 s/mm(2)) were added to the previously reviewed images and the same radiologists sorted the confidence levels.

RESULTS

A total of 26 lesions (0.7-3.5 cm) from 16 patients were confirmed to be perilesional recurrences of HCC. The area under the receiver operating characteristic curve (A(z)) for the second interpretation session (0.826) was not significantly different (P = 0.299) from that of the first session (0.859). The overall sensitivity was increased from 85% to 92%, but the specificity decreased from 65% to 50% after adding DWI.

CONCLUSION

The addition of DWI has the potential to improve sensitivity, but not the overall diagnostic accuracy, in the assessment of perilesional recurrence of HCCs after chemoembolization.

Magnetic resonance measurement of diffusion in the abdomen

Diffusion-weighted (DW) magnetic resonance imaging is an emerging noninvasive technique increasing its spectrum of use in the abdomen. Diffusion-weighted imaging has been used as add-on to routine abdominal protocol because it may potentially substitute contrast-enhanced imaging in cases under risk of nephrogenic systemic fibrosis. The apparent diffusion coefficient (ADC) images calculated from DW images enable qualitative and quantitative evaluations of tissue water mobility and functional environment because of changes in intracellular, extracellular, and intravascular tissue compartments. This article presents the basic physics of the ADC measurement, the techniques for performing ADC measurements of the liver and the pancreas, and the clinical applications of DW imaging.

Diffusion-weighted magnetic resonance imaging of the pancreas

Diffusion-weighted imaging (DWI) assesses the random motion of the water protons. The technique is more frequently used in body imaging, and recent investigations showed its use in pancreatic imaging. Diffusion-weighted imaging can be helpful as a complementary imaging method in the differentiation between mass-forming focal pancreatitis and pancreatic adenocarcinoma. The apparent diffusion coefficient (ADC) values derived from DWI can distinguish between simple pancreatic cyst, inflammatory cysts, and cystic neoplasms of the pancreas. Presence of parenchymal fibrosis in chronic pancreatitis causes diffusion restriction and results in lower ADC values on baseline DWI. The ADC values reveal either delayed peak after secretin stimulation or lower peak values in patients with early chronic pancreatitis, which may be helpful to depict chronic pancreatitis in its earliest stage. In this paper, we reviewed the technical aspects of DWI and its use in pancreatic imaging.