MR imaging of the pancreas: a practical approach

Automated whole-volume measurement of CT fat fraction of the pancreas: correlation with Dixon MR imaging

OBJECTIVES

This study aimed to assess the feasibility of pancreatic steatosis quantification by automated whole-volume measurement of the fat fraction of the pancreas on CT in comparison to MRI using proton-density fat fraction (PDFF) techniques.

METHODS

Fifty-nine patients who underwent both CT and MRI were analyzed. Automated whole-volume measurement of pancreatic fat on unenhanced CT was performed by a histogram analysis with local thresholding. Three sets of CT fat volume fraction (FVF) (%) values with thresholds of -30 Hounsfield unit (HU), -20 HU and -10 HU were compared to MR-FVF (%) values measured on a PDFF map.

RESULTS

The median -30 HU CT-FVF, -20 HU CT-FVF, -10 HU CT-FVF and MR-FVF values of the pancreas were 8.6% (interquartile range (IQR), 11.3), 10.5% (IQR, 13.2), 13.4% (IQR, 16.1) and 10.9% (IQR, 9.7), respectively. The -30 HU CT-FVF (%), -20 HU CT-FVF (%) and -10 HU CT-FVF (%) of the pancreas showed a significant positive correlation with the MR-FVF (%) of the pancreas (ρ = 0.898, p < 0.001, ρ = 0.905, p < 0.001, ρ = 0.909, p < 0.001, respectively). The -20 HU CT-FVF (%) displayed reasonable agreement with the MR-FVF (%) with a low absolute fixed bias (mean difference, 0.32%; limit of agreement from -10.1 to 10.7%).

CONCLUSION

The automated whole-volume measurement of the CT fat fraction of the pancreas using the threshold CT attenuation value of -20 HU may be a feasible, non-invasive, and convenient technique for quantifying pancreatic steatosis.

ADVANCES IN KNOWLEDGE

CT-FVF value of the pancreas had a positive correlation with the MR-FVF value. The -20 HU CT-FVF may be a convenient technique for quantifying pancreatic steatosis.

Quantification of pancreas fat on dual-energy computed tomography: comparison with six-point Dixon magnetic resonance imaging

OBJECTIVES

Although it is important to quantify the degree of fatty degeneration of the pancreas, it is difficult to make such a quantification using conventional computed tomography (CT). The present study evaluated the feasibility of pancreatic fat quantification by dual-energy CT (DECT) compared with T2*-corrected six-point Dixon magnetic resonance imaging (MRI).

MATERIALS AND METHODS

Twenty-eight patients who underwent both DECT (100 and 150 kVp) and Dixon MRI without the use of contrast agents were analyzed. The region of interest (ROI) was placed at the head and body/tail of the pancreas on fat volume fraction (FVF) maps generated using the multi-material decomposition (MMD) algorithm on DECT. The FVF (%) of pancreatic parenchyma measured by DECT (CT-FVF) was compared with that measured on FVF maps calculated using Dixon MRI (MR-FVF) using the Spearman rank correlation coefficient.

RESULTS

The median CT-FVF (%) values of the head and body/tail of the pancreas on DECT were 14.2% (range 0.1-81.2%) and 9.4% (range 0-40.8%), respectively. The median MR-FVF (%) values of the head and body/tail of the pancreas on Dixon MRI were 12.2% (range 1.2-80.9%) and 8.1% (range 0.3-43.7%), respectively. CT-FVF (%) measured by DECT showed a significant correlation with the MR-FVF (%) measured by Dixon MRI in the head of the pancreas (ρ = 0.631, P < 0.001) as well as the body/tail of the pancreas (ρ = 0.526, P = 0.004).

CONCLUSION

DECT may be useful for quantifying the degree of fatty degeneration of the pancreas.

MRI-Based Upper Abdominal Organs-at-Risk Atlas for Radiation Oncology

PURPOSE

The purpose of our study was to provide a guide for identification and contouring of upper abdominal organs-at-risk (OARs) in the setting of online magnetic resonance imaging (MRI)-guided radiation treatment planning and delivery.

METHODS AND MATERIALS

After a needs assessment survey, it was determined that an upper abdominal MRI-based atlas of normal OARs would be of benefit to radiation oncologists and radiation therapists. An anonymized diagnostic 1.5T MRI from a patient with typical upper abdominal anatomy was used for atlas development. Two MRI sequences were selected for contouring, a T1-weighted gadoxetic acid contrast-enhanced MRI acquired in the hepatobiliary phase and axial fast imaging with balanced steady-state precession. Two additional clinical MRI sequences from commercial online MRI-guided radiation therapy systems were selected for contouring and were included in the final atlas. Contours from each data set were completed and reviewed by radiation oncologists, along with a radiologist who specializes in upper abdominal imaging, to generate a consensus upper abdominal MRI-based OAR atlas.

RESULTS

A normal OAR atlas was developed, including recommendations for contouring. The atlas and contouring guidance are described, and high-resolution MRI images and contours are displayed. OARs, such as the bile duct and biliary tree, which may be better seen on MRI than on computed tomography, are highlighted. The full DICOM/DICOM-RT MRI images from both the diagnostic and clinical online MRI-guided radiation therapy systems data sets have been made freely available, for educational purposes, at econtour.org.

CONCLUSIONS

This MRI contouring atlas for upper abdominal OARs should provide a useful reference for contouring and education. Its routine use may help to improve uniformity in contouring in radiation oncology planning and OAR dose calculation. Full DICOM/DICOM-RT images are available online and provide a valuable educational resource for upper abdominal MRI-based radiation therapy planning and delivery.

CT and MR features that can help to differentiate between focal chronic pancreatitis and pancreatic cancer

Diagnosis of a focal pancreatic mass in routine clinical practice can be a challenge because patients with chronic pancreatitis may present with symptoms and imaging findings that can be difficult to distinguish from pancreatic cancer. Markers, such as cancer antigen 19-9 and carcinoembryonic antigen, are helpful if abnormal, but normal values do not rule out pancreatic cancer. One of the strongest complicating factors is that chronic pancreatitis is a risk factor for pancreatic cancer. Transition of chronic pancreatitis to pancreatic cancer is relatively rare, but it normally has a poor prognosis because diagnosis is often delayed. From a radiologic diagnosis perspective, the classic so-called double-duct sign is helpful. This sign is considered a hallmark sign of pancreatic cancer on magnetic resonance cholangiopancreatography, but it can also be identified in patients with chronic pancreatitis or with other conditions. A number of additional imaging findings or signs are, therefore, necessary. The aim of this article was to describe the strong CT and MR imaging features or integrated imaging features that can help to differentiate between pancreatic cancer and focal chronic pancreatitis.

Imaging in chronic pancreatitis: State of the art review

Chronic pancreatitis (CP) is an important gastrointestinal cause of morbidity worldwide. It can severely impair the quality of life besides life-threatening acute and long-term complications. Pain and pancreatic exocrine insufficiency (leading to malnutrition) impact the quality of life. Acute complications include pseudocysts, pancreatic ascites, and vascular complications. Long-term complications are diabetes mellitus and pancreatic cancer. Early diagnosis of CP is crucial to alter the natural course of the disease. However, majority of the cases are diagnosed in the advanced stage. The role of various imaging techniques in the diagnosis of CP is discussed in this review.

Sinistral Portal Hypertension in Acute Pancreatitis: A Magnetic Resonance Imaging Study

OBJECTIVE

The aim of the study was to study the prevalence and characteristics of sinistral portal hypertension (SPH) in acute pancreatitis (AP) and its correlation with the severity of AP.

METHODS

Retrospectively studied 633 patients with AP admitted to our institution and underwent magnetic resonance imaging (MRI). Diagnosis of SPH was based on clinical manifestations, laboratory tests, and MRI. The venous system and pancreatitis were evaluated on T1 weighted imaging, T2 weighted imaging, and dynamic-enhancement MRI. Data on patients' demographics, etiology, organ failure, MR severity index, and clinical outcomes were all collected.

RESULTS

The SPH was detected in 21 patients (3.3%, 21/633). There was no statistical difference in organ failure between patients with SPH and without SPH (P > 0.05). The prevalence of SPH in males and females was 5.1% (17/336) versus 1.3% (4/297) (χ(2) = 6.775, P = 0.009), in edematous and necrotizing AP was 0.4% (2/510) versus 15.5% (19/123) (χ(2) = 65.413, P = 0.000), and in mild, moderate, and severe AP, based on MR severity index, were 0.6% (2/334) versus 2.9% (8/276) versus 47.8% (11/23) (χ(2) = 55.977, P = 0.000), respectively.

CONCLUSIONS

The SPH rarely occurs in AP, and its risk is higher in males. Its presence is strongly associated with the local conditions of pancreatitis.

Spleen and splenic vascular involvement in acute pancreatitis: an MRI study

Background

To investigate the spleen and splenic vascular involvement in acute pancreatitis (AP) and their correlations with the severity of AP using magnetic resonance imaging (MRI).

Methods

MRI of 239 patients with AP was retrospectively reviewed to assess splenic and splenic vascular complications, and the severity of AP. The severity of AP was graded by the MRI severity index (MRSI) and the New Revised Classification of AP 2012. The intravoxel incoherent motion (IVIM) parameters (D, D*, and f) of spleen were measured. Thirty-five subjects without pancreatic and splenic disorders were enrolled as controls for IVIM parameters.

Results

Among the 239 patients with AP, splenomegaly (16.7%), splenic infarction (0.4%), splenic vein thrombosis (4.2%), phlebitis (7.5%) and arteritis (4.2%) were observed. Splenic vascular involvement was positively correlated with the severity of AP based on both the MRSI and the New Revised Classification of AP 2012 (P<0.05). In the control and AP groups, the splenic f values were (0.164±0.074) vs. (0.210±0.095) (P=0.023) respectively. In AP patients with and without splenomegaly, f = (0.240±0.091) vs. (0.203±0.095) (P<0.001).

Conclusions

Splenic vascular involvement and splenomegaly were common in AP. The vascular involvement was associated with the severity of AP. This complication should be considered when severity and prognosis of AP are assessed. Quantitative analysis of the spleen with IVIM might be a useful imaging biomarker for splenic perfusion changes in AP, especially in those with splenomegaly.

Preoperative Evaluation of a Pancreas Mass: Diagnostic Options

As modern abdominal imaging equipment advances, pancreatic lesion detection improves. Most of these lesions are incidental, and present a conundrum to the clinician and create great anxiety to the patient until a final diagnosis is made. For the practicing physician, the plethora of diagnostic options is overwhelming. The relevant question is, what is the most efficient algorithm to follow and to arrive at a timely and accurate diagnosis. This article presents a logical approach to the initial evaluation of a pancreatic lesion to get the most information possible with the least amount of testing, and to avoid duplicative measures.

Diagnostic performance of imaging modalities in chronic pancreatitis: a systematic review and meta-analysis

OBJECTIVES

Obtain summary estimates of sensitivity and specificity for imaging modalities for chronic pancreatitis (CP) assessment.

METHODS

A systematic search was performed in Cochrane Library, MEDLINE, Embase and CINAHL databases for studies evaluating imaging modalities for the diagnosis of CP up to September 2016. A bivariate random-effects modeling was used to obtain summary estimates of sensitivity and specificity.

RESULTS

We included 43 studies evaluating 3460 patients. Sensitivity of endoscopic retrograde cholangiopancreatography (ERCP) (82%; 95%CI: 76%-87%) was significant higher than that of abdominal ultrasonography (US) (67%; 95%CI: 53%-78%; P=0.018). The sensitivity estimates of endoscopic ultrasonography (EUS), magnetic resonance imaging (MRI), and computed tomography (CT) were 81% (95%CI: 70%-89%), 78% (95%CI: 69%-85%), and 75% (95%CI: 66%-83%), respectively, and did not differ significantly from each other. Estimates of specificity were comparable for EUS (90%; 95%CI: 82%-95%), ERCP (94%; 95%CI: 87%-98%), CT (91%; 95% CI: 81%-96%), MRI (96%; 95%CI: 90%-98%), and US (98%; 95%CI: 89%-100%).

CONCLUSIONS

EUS, ERCP, MRI and CT all have comparable high diagnostic accuracy in the initial diagnosis of CP. EUS and ERCP are outperformers and US has the lowest accuracy. The choice of imaging modality can therefore be made based on invasiveness, local availability, experience and costs.

KEY POINTS

• EUS, ERCP, MRI and CT have high diagnostic sensitivity for chronic pancreatitis • Diagnostic specificity is comparable for all imaging modalities • EUS and ERCP are outperformers and US has the lowest accuracy • The choice of imaging can be made based on clinical considerations.

The normal transverse mesocolon and involvement of the mesocolon in acute pancreatitis: an MRI study

Objective

To study the MRI findings of the normal transverse mesocolon and the involvement of the mesocolon in acute pancreatitis (AP) as well as the relationship between the involvement of the mesocolon and the severity of AP.

Materials and Methods

Forty patients without pancreatic disorders were retrospectively analyzed to observe the normal transverse mesocolon using MRI; 210 patients with AP confirmed by clinical and laboratory tests were retrospectively analyzed using MRI to observe transverse-mesocolon involvement (TMI). The severity of TMI was recorded as zero points (no abnormalities and transverse-mesocolon vessel involvement), one point (linear and patchy signal in the transverse mesocolon) or two points (transverse-mesocolon effusion). The AP severity was graded by the MRI severity index (MRSI) and the Acute Physiology And Chronic Healthy Evaluation II (APACHE II) scoring system. The correlations of TMI with MRSI and APACHE-II were analyzed.

Results

In a normal transverse mesocolon, the display rates of the middle colic artery, the middle colic vein and the gastrocolic trunk on MRI were 95.0%, 82.5% and 100.0%, respectively. Of the 210 patients with AP, 130 patients (61.9%) had TMI. According to the TMI grading, 40%, 39% and 20% of the patients were graded at zero, one and two points, respectively. TMI was strongly correlated with the MRSI score (r = 0.759, P = 0.000) and the APACHE-II score (r = 0.384, P = 0.000).

Conclusion

MRI could be used to visualize transverse-mesocolon involvement. The severity of TMI could reflect that of AP in the clinical setting and imaging. TMI might be a supplementary indicator of the severity of AP.

MR imaging of the pancreas

Magnetic resonance (MR) imaging of the pancreas is useful as both a problem-solving tool and an initial imaging examination of choice. With newer imaging sequences such as diffusion-weighted imaging, MR offers improved ability to detect and characterize lesions and identify and stage tumors and inflammation. MR cholangiopancreatography can be used to visualize the pancreatic and biliary ductal system. In this article, the use of MR to evaluate the pancreas, including recent advances, is reviewed and the normal appearance of the pancreas on different imaging sequences, as well as inflammatory diseases, congenital abnormalities, and neoplasms of the pancreas, are discussed.

Diagnostic evaluation of solid pancreatic masses

Determining the etiology of a solid pancreatic lesion is a critical first step toward developing an appropriate treatment plan for patients with a benign or malignant pancreatic mass. Technological advances in cross-sectional and endoscopic imaging modalities offer pancreatic imaging options with degrees of resolution that were not available even 15-20 years ago. In most cases, the nature of a solid pancreatic mass can be determined using computerized tomography, magnetic resonance imaging, and endoscopic ultrasound with fine-needle aspiration. Knowledge about the basics of these modalities, as well as their strengths and limitations, plays an important role in understanding how patients with solid pancreatic masses should be evaluated.

Quantitative assessment of pancreatic fat by using unenhanced CT: pathologic correlation and clinical implications

PURPOSE

To assess the relationship between computed tomographic (CT) indexes and histologically measured pancreatic fat in surgical specimens and to evaluate patients with impaired glucose metabolism in a clinical setting.

MATERIALS AND METHODS

This retrospective study was institutional review board approved and informed consent was waived. The hospital database was searched for records from November 2008 to April 2009, and 62 patients (42 men and 20 women; mean age, 61.4 years; age range, 21-81 years) who underwent CT within 1 month before pancreatectomy were identified. The histologic pancreatic fat fraction (area ratio of fat to total tissue times 100%) was measured in nontumorous pancreatic tissue. Attenuation was measured in three regions of interest in the pancreas and the spleen on nonenhanced CT images. The difference between pancreatic and splenic attenuation and the pancreas-to-spleen attenuation ratio were calculated. Visceral fat area at the level of the umbilicus was measured on the CT images. Spearman correlation coefficients (ρ) were calculated to examine the correlation between the CT indexes or visceral fat area and the histologic pancreatic fat fraction. A multivariate logistic regression model was used to determine whether CT attenuation indexes and patient age, sex, and visceral fat correlated with impaired glucose metabolism (ie, impaired glucose tolerance, impaired fasting glucose, or presence of diabetes).

RESULTS

The histologic pancreatic fat fraction ranged from 0% to 65.3% and was significantly correlated with the difference between pancreatic and splenic attenuation (ρ = -0.622, P < .01) and the pancreas-to-spleen attenuation ratio (ρ = -0.616, P < .01). The visceral fat area was not correlated with the histologic pancreatic fat fraction (ρ = 0.09, P = .50). The CT attenuation indexes were significant and independent variables predictive of impaired glucose metabolism after adjusting for age, sex, and visceral fat.

CONCLUSION

Pancreatic fat can be quantified by using CT, and CT attenuation indexes that are applied to the quantification of pancreatic fat are significantly associated with clinical assessment of impaired glucose metabolism.

Morphological and functional evaluation of chronic pancreatitis with magnetic resonance imaging

Magnetic resonance imaging (MRI) techniques for assessment of morphology and function of the pancreas have been improved dramatically the recent years and MRI is very often used in diagnosing and follow-up of chronic pancreatitis (CP) patients. Standard MRI including fat-suppressed T1-weighted and T2-weighted imaging techniques reveal decreased signal and glandular atrophy of the pancreas in CP. In contrast-enhanced MRI of the pancreas in CP the pancreatic signal is usually reduced and delayed due to decreased perfusion as a result of chronic inflammation and fibrosis. Thus, morphological changes of the ductal system can be assessed by magnetic resonance cholangiopancreatography (MRCP). Furthermore, secretin-stimulated MRCP is a valuable technique to evaluate side branch pathology and the exocrine function of the pancreas and diffusion weighted imaging can be used to quantify both parenchymal fibrotic changes and the exocrine function of the pancreas. These standard and advanced MRI techniques are supplementary techniques to reveal morphological and functional changes of the pancreas in CP. Recently, spectroscopy has been used for assessment of metabolite concentrations in-vivo in different tissues and may have the potential to offer better tissue characterization of the pancreas. Hence, the purpose of the present review is to provide an update on standard and advanced MRI techniques of the pancreas in CP.

Multimodality imaging of pancreatic cancer-computed tomography, magnetic resonance imaging, and positron emission tomography

Pancreatic adenocarcinoma continues to have a dismal prognosis, with curative surgery (resection with negative margins) possible in only a small percentage of patients. Not only does radiological imaging play a major role in diagnosing the primary lesion at presentation, but it is also crucial for staging of locoregional disease and distant metastases, both of which are critical for selecting appropriate candidates for surgery. Over the last 2 decades, computed tomography has become the dominant imaging modality for both the diagnosis and staging of pancreatic cancer, with advances in multidetector computed tomography technology improving the ability to identify small tumors and demonstrate subtle degrees of vascular involvement by tumor. However, magnetic resonance imaging and positron emission tomography are now playing an increasing role in pancreatic cancer imaging. These 3 imaging modalities each have specific strengths and benefits and should be used in a complementary fashion.

Gallbladder patterns in acute pancreatitis: an MRI study

RATIONALE AND OBJECTIVES

The aim of this study was to assess the gallbladder patterns on magnetic resonance imaging (MRI) associated with acute pancreatitis (AP).

MATERIALS AND METHODS

There were 197 patients with AP, all of whom had undergone abdominal MRI. AP was categorized as either edematous or necrotizing according to its findings on MRI and graded as mild (0-3 points), moderate (4-6 points), or severe (7-10 points) according to the magnetic resonance severity index. The changes to the walls and dimensions of the gallbladder and common bile duct, in addition to the presence of biliary stones and pericholecystic fluid, were noted and compared with the severity of AP on the basis of the magnetic resonance severity index.

RESULTS

Of the 197 patients with AP, 81% were classified as edematous and 19% as necrotizing on MRI. There were 35%, 59%, and 6% of patients with mild, moderate, and severe AP according to the magnetic resonance severity index, respectively. Seventy-six percent of patients had at least one gallbladder abnormality on MRI, including a thickened gallbladder wall (42%), pericholecystic fluid (38%), gallbladder stones (35%), an enlarged gallbladder (24%), dilatation of the common bile duct (16%), and subserosal edema (15%). Eighty-nine percent of patients (34 of 38) with necrotizing AP had gallbladder abnormalities, which was significantly higher than the 72% of patients (115 of 159) with edematous AP (P < .05). The prevalence of gallbladder abnormalities was 64% in patients with mild AP, 81% in those with moderate AP, and 91% in those with severe AP (P < .05 among the three groups).

CONCLUSIONS

Most patients with AP have gallbladder abnormalities on MRI, including a thickened gallbladder wall and pericholecystic fluid. The prevalence of gallbladder abnormalities has a positive correlation with the severity of AP on MRI.

Diffusion-weighted MR imaging of solid and cystic lesions of the pancreas

Diffusion-weighted magnetic resonance (MR) imaging is increasingly used in the detection and characterization of pancreatic lesions. Diffusion-weighted imaging may provide additional information to radiologists evaluating patients who have cystic or solid neoplasms of the pancreas. Because of greater freedom of motion of water molecules in fluid-rich environments, simple cysts in the pancreas have higher signal intensity on diffusion-weighted images with a b value of 0 sec/mm2 and lower signal intensity on high-b-value images. High apparent diffusion coefficient (ADC) values can be obtained on ADC maps because of the T2 “shine-through” effect. In contrast, solid neoplasms of the pancreas show increased signal intensity relative to the pancreas on diffusion-weighted images with a b value of 0 sec/mm2 and relatively high signal intensity on high-b-value images. Diffusion-weighted imaging can help detect solid pancreatic neoplasms with extremely dense cellularity or extracellular fibrosis by demonstrating significantly low ADC values, and these neoplasms may be better detected on diffusion-weighted MR images because of better contrast, although the resolution is generally worse. However, diffusion-weighted imaging may not be capable of helping definitively characterize solid lesions as inflammatory or neoplastic because of an overlap in ADC values between the two types. For example, it is difficult to distinguish poorly differentiated pancreatic adenocarcinoma from mass-forming pancreatitis at diffusion-weighted imaging because of similarly low ADC values attributed to dense fibrosis.

Diagnostic accuracy of endoscopic ultrasonography in patients with inconclusive magnetic resonance imaging diagnosis of biliopancreatic abnormalities

AIM

To determine the sensitivity and specificity of endoscopic ultrasonography (EUS) in patients with inconclusive magnetic resonance imaging/magnetic resonance cholangiopancreatography (MRI/MRCP) in pancreatobiliary abnormalities.

METHODS

During 10 months, patients with pancreatobiliary diseases referred to endoscopic retrograde cholangiopancreatography (ERCP) because of inconclusive MRI/MRCP diagnosis were scheduled to undergo endoscopic ultrasonography. Patients were divided into four major groups: patients with (i) resectable periampullary neoplasms who were referred to a surgeon, (ii) unresectable periampullary cancer who underwent ERCP for biliary stenting, (iii) bile duct stone who were referred to ERCP for stone extraction, and (iv) normal pancreatobiliary tract. Reference standards for comparison were ERCP, surgery, a biopsy confirming malignancy, or the clinical course during follow up (at least 12 months) in cases without evidences of malignancy.

RESULTS

One hundred and seven patients (51 men; mean [SD] age 60.0 [15.5]) were included in the study. Final diagnoses were common bile duct (CBD) stone (n = 24), periampullary neoplasms (n = 46), others (n = 23) and no pathologic findings (n = 14). EUS determined the staging for clinical decision-making in 47 patients with neoplasms which showed that tumors in 34 patients (79.1%) were unresectable (advanced stage). After EUS, 47 patients (43.9%) did not require ERCP. The accuracy of EUS for the diagnosis of CBD stone and periampullary neoplasms were 96.3% and 99.1%, respectively.

CONCLUSIONS

EUS is a useful modality in cases of inconclusive MRI/MRCP indicating pancreatobiliary disorders.

Imaging in staging and management of pancreatic ductal adenocarcinoma

Pancreatic cancer is a relatively common malignancy of the gastrointestinal tract for which complete surgical excision remains the only curative option. Being infiltrative in nature and bearing a complex anatomical relationship with various organs, peritoneal ligaments and vascular structures, accurate anatomical staging is key in treatment of these patients. In this article, we will discuss and provide a brief overview of anatomy and use of imaging in staging pancreatic cancer.

Advanced imaging of chronic pancreatitis

Chronic pancreatitis is characterized by continuing inflammation, destruction, and irreversible morphological changes in the pancreatic parenchyma and ductal anatomy. These changes lead to chronic pain and/or loss of function. Although these definitions are simple, the clinical diagnosis of chronic pancreatitis remains difficult to make, especially for early disease. Routine imaging modalities such as transabdominal ultrasound and standard CT scans are insensitive for depicting early disease, and detect only advanced chronic pancreatitis. Advances in imaging modalities including CT, MRI with gadolinium contrast enhancement, MRI with magnetic resonance cholangiopancreatography (MRI/MRCP), MRI/MRCP with secretin-stimulation (S-MRCP), endoscopic retrograde cholangiopancreatography (ERCP), and endoscopic ultrasound (EUS) allow earlier diagnosis of chronic pancreatitis. This article reviews the recognized findings, advantages, and disadvantages of the various imaging modalities in the management of chronic pancreatitis, specifically CT, MRI with or without MRCP and/or S-MRCP, ERCP, and EUS.

Morphine- and glucagon-augmented magnetic resonance cholangiopancreatography to evaluate living liver donors

The purpose of this study was to investigate the effectiveness of the combined use of intravenous morphine and intramuscular glucagon in improving magnetic resonance cholangiopancreatography (MRCP) image quality in donors for living-related liver transplantation. Sixteen healthy donor candidates underwent an MRCP study. Coronal, single-shot, fast spin-echo, heavily T2-weighted dynamic MRCP images were obtained before and 3 minutes after the intravenous administration of morphine HCl with a dose of 0.04 mg/kg. Thirty minutes after the injection of morphine, intramuscular glucagon was used. Another MRCP image of the same pulse sequence was generated 15 minutes after the injection of glucagon with a dose of 1 mg. The diameter, signal intensity, and number of branches of bile ducts in MRCP images taken immediately before and after the injection of morphine and after the injection of glucagon (plus delayed morphine effects) were compared and analyzed. In all 16 donor candidates, the diameters of the right and left hepatic ducts, common bile duct, and main pancreatic duct were significantly increased (P < 0.05) in the MRCP images taken 3 minutes after the injection of morphine and 15 minutes after the injection of glucagon (plus delayed morphine effects) in comparison with MRCP images taken before any drug administration. The qualitative grading scores of the signal intensity and order of branches of bile ducts revealed improvements in the MRCP images after the injection of glucagon (plus delayed morphine effects; P < 0.05). In conclusion, combining the intravenous administration of low-dose morphine and the intramuscular use of glucagon before MRCP examination improves the visualization of the nondilated biliary ductal anatomy, which is important for the preoperative biliary evaluation of donor candidates for living-related liver transplantation.

Pancreatic ductal adenocarcinoma: ultrasound, computed tomography, and magnetic resonance imaging features

The technologies of computed tomography, magnetic resonance, and ultrasound (transabdominal and endoscopic) have advanced considerably in recent years, having a major impact on the management of pancreatic cancer, guiding surgery for the potential of cure, and avoiding needless surgery in those patients who are unresectable. Knowledge of how these modalities should be utilized, how they can be optimized, and the appearance of ductal adenocarcinoma on each modality are crucial for them to be used effectively and accurately.

Chronic pancreatitis: ultrasound, computed tomography, and magnetic resonance imaging features

Chronic pancreatitis is a progressive, irreversible inflammatory and fibrosing disease of the pancreas with clinical manifestations of chronic abdominal pain, weight loss, and permanent pancreatic exocrine and endocrine insufficiency. In the United States, a long history of heavy alcohol consumption is the most common cause of chronic pancreatitis. This review discusses the different modalities such as computed tomography, transabdominal and endoscopic ultrasound, magnetic resonance imaging/magnetic resonance cholangiopancreatography, and endoscopic retrograde cholangiopancreatography available to image chronic pancreatitis, along with their advantages and limitations. In addition, topics such as groove pancreatitis and autoimmune pancreatitis are examined, along with a discussion of distinguishing chronic pancreatitis from pancreatic adenocarcinoma.

Pancreatic adenocarcinoma: diagnosis and staging using multidetector-row computed tomography (MDCT) and magnetic resonance imaging (MRI)

Pancreatic adenocarcinoma continues to be a leading cause of cancer death in the Western world and is amongst the leading gastrointestinal cancers. The incidence of pancreatic cancer has been stable or slowly rising in the past few decades. Overall the prognosis is poor with 5-year survival rates still under 5%. Therefore early detection and accurate staging of these tumors is crucial for optimal treatment.

Magnetic resonance imaging in the detection of pancreatic neoplasms

Recently, with the rapid scanning time and improved image quality, outstanding advances in magnetic resonance (MR) methods have resulted in an increase in the use of MRI for patients with a variety of pancreatic neoplasms. MR multi-imaging protocol, which includes MR cross-sectional imaging, MR cholangiopancreatography and dynamic contrast-enhanced MR angiography, integrates the advantages of various special imaging techniques. The non-invasive all-in-one MR multi-imaging techniques may provide the comprehensive information needed for the preoperative diagnosis and evaluation of pancreatic neoplasms. Pancreatic neoplasms include primary tumors and pancreatic metastases. Primary tumors of the pancreas may be mainly classified as ductal adenocarcinomas, cystic tumors and islet cell tumors (ICT). Pancreatic adenocarcinomas can be diagnosed in a MRI study depending on direct evidence or both direct and indirect evidence. The combined MRI features of a focal pancreatic mass, pancreatic duct dilatation and parenchymal atrophy are highly suggestive of a ductal adenocarcinoma. Most cystic neoplasms of the pancreas are either microcystic adenomas or mucinous cystic neoplasms. Intraductal papillary mucinous tumors are the uncommon low-grade malignancy of the pancreatic duct. ICT are rare neoplasms arising from neuroendocrine cells in the pancreas or the periampullary region. ICT are classified as functioning and non-functioning. The most frequent tumors to metastasize to the pancreas are cancers of the breast, lung, kidney and melanoma. The majority of metastases present as large solitary masses with well-defined margins.

IRM et maladies pancréatiques

Magnetic resonance (MR) imaging of the pancreas has undergone a major change because it can provide noninvasive images of the pancreatic ducts and the parenchyma. MR cholangiopancreatography (MRCP) enables detection of anatomic variants such as pancreas divisum. Although contrast material-enhanced CT is still considered the gold standard in acute pancreatitis and for the detection of calcifications in chronic pancreatitis, MR imaging and secretin-enhanced MRCP are useful in evaluating pseudocysts and pancreatic disruption. The role of MR is still debated in pancreatic neoplasms except the cystic lesions where MR imaging provides critical information regarding the lesion's content and a possible communication with the pancreatic ducts. MRCP and MR of the pancreas are also useful in identifying other pancreatic diseases such as lymphoplasmocytic pancreatitis and groove pancreatitis.

Current treatment strategies for pancreatic cancer in the elderly

Pancreatic cancer, which is responsible for >90% of exocrine pancreatic tumours, is typically a disease of the elderly (> or =70 years of age). However, older patients are less likely to be staged than younger patients despite having a worse overall 5-year survival rate than their younger counterparts. Various radiological, ultrasonographic and endoscopic investigations are used not only as diagnostic tools but also to accurately stage the cancer for possible surgery. Many patients with pancreatic cancer have mutations of the K-ras oncogene, and various tumour suppressor genes are also inactivated. Pancreas resection can be performed in elderly resectable patients without excess mortality, even in those >80 years of age. However, treatment for locally advanced, unresectable and metastatic pancreatic cancer is palliative. Fluorouracil-based chemoradiation for locally advanced or unresectable cancer, and gemcitabine for patients with metastatic disease, can result in clinical benefits. Placement of a stent in the biliary tract has been shown to improve symptoms of obstructive jaundice or ascites, as well as quality of life. As molecular targets are identified, interventions with targeted specific agents may improve tumour control. However, further studies will be needed to demonstrate whether or not various agents targeting signal transduction pathways or nuclear transcription factors are useful for elderly patients with advanced pancreatic cancer.

MRI of adenocarcinoma of the pancreas

OBJECTIVE

CT is the established imaging technique for evaluation of pancreatic adenocarcinoma. MRI, however, can play a major role in this disease. The objective of this study is to illustrate the strengths of MRI for evaluating pancreatic adenocarcinoma.

CONCLUSION

The superior soft-tissue contrast of MRI compared with CT is useful in the detection and characterization of non-contour-deforming pancreatic masses. MRI compared with CT may be more sensitive in the detection of distant disease, better for defining appropriate surgical candidates, and better for characterizing small liver metastases and peritoneal and omental metastases.

Does secretin-stimulated MRCP predict exocrine pancreatic insufficiency?: A comparison with noninvasive exocrine pancreatic function tests

BACKGROUND

Data on magnetic resonance cholangiopancreatography with secretin stimulation (S-MRCP) for the assessment of exocrine pancreatic insufficiency (EPI) are limited. We compared pancreatic function tests with the findings of S-MRCP in patients with chronic pancreatitis (CP) and disease controls.

METHODS

S-MRCP was performed in 23 patients (18 CP, 5 disease controls). MRCP images were analyzed for secretin-induced duodenal liquid filling (0=no filling; 1=duodenal bulb; 2=up to lower flexure; 3=beyond lower flexure). EPI was evaluated by fecal elastase, fecal fat concentration, and a 13C mixed chain triglyceride breath test. Clinically relevant EPI was stated if 2 of 3 tests were pathologic.

RESULTS

EPI was diagnosed in 10 of 18 patients with CP. Patients without EPI showed either grade 2 (n=4) or grade 3 (n=9) duodenal filling, whereas only 1/10 patients with EPI showed grade 3 duodenal filling. Sensitivity and specificity of S-MRCP for the diagnosis of EPI were 69% and 90%, respectively.

CONCLUSIONS

Assessment of duodenal filling should be performed in patients who undergo S-MRCP for the evaluation of pancreatic morphology. However, minor degrees of duodenal filling are equivocal and require further diagnostic evaluation.

Pancreatic and peripancreatic diseases mimicking primary pancreatic neoplasia

A variety of anatomic variants and pathologic conditions in and around the pancreas may simulate primary pancreatic neoplasia at routine abdominal cross-sectional imaging. An ambiguous lesion whose appearance suggests a pancreatic origin requires a broad differential diagnosis that can subsequently be narrowed on the basis of both clinical history and features at optimal computed tomography (CT) and magnetic resonance (MR) imaging. Pancreas-specific multidetector CT and MR imaging techniques with thin collimation, multiplanar and multiphasic scans, and newly introduced curved planar reformation may help avoid potential diagnostic pitfalls. These techniques can help identify and characterize a mass in multiple viewing planes, thereby helping distinguish a true pancreatic neoplasm from peripancreatic adenopathy or from a tumor of the adjacent duodenum or small bowel. They can also help determine the cause of a tumor. It is important that the radiologist be familiar with the wide spectrum of anatomic variants and disease entities that can mimic primary pancreatic neoplasia in order to initiate the appropriate lesion-specific work-up and treatment and avoid unnecessary tests or procedures, including surgery.

Fentanyl-augmented MRCP

BACKGROUND

Drugs such as secretin and morphine have been used to augment the visualization of magnetic resonance cholangiopancreatography (MRCP). This study investigated the effectiveness of intravenous administration of a synthetic opioid, fentanyl, in improving the MRCP image quality.

METHODS

Thirty consecutive patients with a provisional diagnosis of benign biliary and/or pancreatic disease underwent MRCP. Coronal single-shot fast spin-echo heavily T2-weighted dynamic MRCP images were generated before and at every minute for 10 min after intravenous administration of fentanyl citrate at a dose of 1.0 mug/kg. Pre- and postinjection images were compared and analyzed qualitatively and quantitatively.

RESULTS

Qualitatively, visualization of intrahepatic bile ducts, common bile duct, and main pancreatic duct improved after fentanyl injection in five (16%), 11 (37%), and 19 (63%) patients, respectively. The pancreatobiliary junction and common channel were visualized better after fentanyl injection in eight of the 18 patients (44%). Quantitatively, signal intensity and diameters of the intrahepatic ducts, common bile duct, and main pancreatic duct measured at corresponding points on pre- and postinjection images showed an increase above preinjection values in 28 (93%), 27 (90%), and 21 (70%) and in 18 (60%), 26 (86%), and 22 (73%), respectively, and these changes were highly significant at all sites (p < 0.001).

CONCLUSIONS

Intravenous administration of fentanyl before MRCP improves qualitative and quantitative visualization of the ductal system anatomy that may be of value in clinical diagnosis and management.

Mangafodipir trisodium-enhanced MR imaging of pancreatic disease

Our study aimed to assess the diagnostic capabilities of mangafodipir trisodium-enhanced MRI for the evaluation of pancreatic disease. Sixty-three patients suspected of having pancreatic disease underwent MRI with a 1.5-T device. After the acquisition of axial and coronal T2-weighted sequences, the MR protocol included T1-weighted fat-suppressed breath-hold SPGR images obtained before and 30 min after the infusion of Mn-DPDP (Teslascan). The detection of a focal pancreatic lesion and its intensity were evaluated in consensus by two observers, who also attempted to characterize each lesion as benign or malignant. The reviewers were blinded to patient identification and all clinical, laboratory and previous imaging findings. MR imaging results were correlated with surgery (n=37), laparoscopy (n=1), biopsy (n=2) and imaging follow-up (n=22). Sixty-two subjects were effectively included in our analysis because one patient was lost to follow-up; final malignant and benign diagnoses were determined in 22 (35%) and 29 (47%) of the patients, respectively. The level of confidence in the diagnosis of the pancreatic lesion was significantly increased by the administration of Mn-DPDP as demonstrated by ROC analysis of unenhanced and post-contrast image sets (P=0.009). Overall, on the basis of observers' readings, MR assessment of pancreatic disease resulted in 57 correct diagnoses (accuracy, 92%) and five (8%) incorrect diagnoses. The sensitivity, specificity, positive predictive value and negative predictive value of the reviewers for the detection of pancreatic lesions and for the differentiation between benign and malignant masses were 91% (95% CI: 84 and 98%), 93% (95% CI: 86 and 99%), 87% (95% CI: 79 and 95%) and 95% (95% CI: 89 and 100%), respectively. Mn-DPDP-enhanced MRI is an effective diagnostic tool for evaluating pancreatic disease.

State-of-the-art computed tomographic and magnetic resonance imaging of the gastrointestinal system

Among the major innovations in radiology of the gastrointestinal (GI) system are the replacement of classic invasive diagnostic methods with noninvasive ones and the improvement in lesion characterization and staging of pancreatobiliary malignancies. Developments in imaging technology have led to many improvements in the field of diagnostic GI radiology. With its fast and thin-section scanning abilities, multidetector-row CT (MDCT) strengthens the place of CT as the most efficient tool to diagnose, characterize, and preoperatively stage pancreatic neoplasms. MR cholangiopancreatography has widely replaced endoscopic retrograde cholangiopancreatography in the diagnosis and staging of pancreatobiliary malignancies. MR imaging, using phased-array or endorectal coils, demonstrates local tumor invasion accurately in rectal cancers and thus allows an improved surgical planning. Virtual colonoscopy with MDCTs is an efficient screening method for colon cancer, and MDCT enterography is becoming the standard imaging technique for many small bowel disorders. The continuing developments in CT and MR technology will most probably further improve the accuracy of these and other imaging applications in the near future.

Magnetic Resonance Imaging of the Pancreas: The Future Is Now

MR imaging has made significant advances in recent years, with an increasingly important role in the detection, characterization, and staging of pancreatic diseases. MRI is appealing as a noninvasive imaging modality as it can evaluate the pancreas, the vasculature, and the pancreaticobiliary ducts in a single examination. Advantages of MRI include its excellent soft tissue contrast resolution and anatomic detail and absence of ionizing radiation. This article reviews the utility of MRI and its use not only as a problem-solving tool but its potential use as a primary examination (similar to CT) in a wide variety of pancreatic diseases.

Imaging and localization of islet-cell tumours of the pancreas on CT and MRI

Islet-cell tumours are neuroendocrine tumours that arise from the endocrine pancreas. They may be associated with a variety of syndromes and are subclassified into functioning and non-functioning tumours. They range from benign to malignant. They demonstrate characteristic features when imaged with both computed tomography (CT) and magnetic resonance imaging (MRI). Sensitivity and specificity, as well as detection of extrapancreatic extension, are generally superior with MRI. However, CT is currently still more readily available to patients. Multiphase, post-contrast series are commended for the evaluation of islet-cell tumours with either modality.

Contrast-enhanced computed tomography in acute pancreatitis: does contrast medium worsen its course due to impaired microcirculation?

BACKGROUND

An early and accurate diagnosis of severe acute (necrotizing) pancreatitis is important to allow timely institution of therapy to limit the extra-pancreatic sequelae of this necrotizing process and to minimize the incidence of super-infection of the necrosis (i.e., progression to infected necrosis). Contrast-enhanced computed tomography (CECT) has become the cornerstone of diagnosis by confirming the clinical diagnosis of severe acute pancreatitis based on the various clinical scoring criteria. Moreover, CECT serves as an anatomic roadmap for guiding radiological and surgical interventions. However, still-controversial experimental studies in animals in the mid-1990s suggested that the use of intravenous radiographic contrast media early in the course of the disease might exacerbate the necrotizing process by further impairing the already compromised pancreatic microcirculation. A series of experimental and clinical studies followed that have both refuted and supported this claim; unfortunately, none is conclusive, and the topic remains, as yet, unresolved.

AIMS

Our objective was to review objectively the available literature found by a Medline search on this subject.

METHODS

Meta-analysis and review.

RESULTS AND CONCLUSION

Our conclusion, after analysis of these studies, is that there are no well-substantiated data that could resolve the controversy. However, several caveats will be offered.

MRI combined with MR cholangiopancreatography versus helical CT in the evaluation of patients with suspected periampullary tumors: a prospective comparative study

PURPOSE

To establish the diagnostic accuracy of MRI including MR cholangiopancreatography (MRCP) compared with helical CT in the differentiation of malignant and benign lesions in the periampullary region.

MATERIAL AND METHODS

Fifty-one patients (27 M, 24 F, mean age 66 years, range 39-86 years) with obstructive jaundice and sonographic evidence of intra- and extrahepatic bile duct dilatation (n=31) or suspicion of periampullary tumor, based on previously performed ultrasound and/or CT examination (n=20), were studied. MRI with MRCP and helical CT were reviewed blindly under standardized conditions. Lesion status (differentiation of malignant versus benign) was rated on a 5-point diagnostic confidence scale. Reference standards for comparison were findings at surgery or laparoscopy and/ or the clinical outcome. The predictive value of imaging findings was determined with multivariate logistic regression analysis.

RESULTS

The areas under the receiver operating characteristic curve were 0.96 for MRI with MRCP and 0.81 for CT (P <0.05). Multivariate analysis of eight imaging variables at MRI indicated that a stricture with malignant characteristics at MRCP was the best predictor of malignancy.

CONCLUSION

MRI with MRCP was significantly more accurate than CT in differentiating between malignant and benign lesions in patients with suspected periampullary tumors, mainly due to the information obtained on the MRCP images of the biliary and pancreatic duct anatomy.

Improved targeting of pancreatic cancer: experimental studies of a new bispecific antibody, pretargeting enhancement system for immunoscintigraphy

PURPOSE

The early detection and diagnosis of pancreatic cancer remains a major clinical challenge in which imaging procedures have a central role. The purpose of this study was to evaluate a pretargeting method with a bispecific PAM4 (bsPAM4; anti-MUC1) antibody for radioimmunoscintigraphy of experimental human pancreatic cancer.

EXPERIMENTAL DESIGN

A bispecific F(ab')(2) antibody was generated from chimeric PAM4 Fab' and murine 734 (anti-indium-diethylenetriaminepentaacetic acid) Fab' fragments and then used in conjunction with 2 peptide haptens ((111)In-IMP-156 and (99m)Tc-IMP-192). Biodistribution studies and radioimmunoscintigraphic imaging properties of the radiolabeled bsPAM4, and pretargeted, radiolabeled peptides were examined in the CaPan1 human pancreatic tumor grown as s.c. xenografts in athymic nude mice. Tumor uptake and tumor:nontumor ratios were compared with a nontargeting irrelevant anti-CD20, bispecific rituximab, radiolabeled peptides alone, and with directly labeled PAM4.

RESULTS

Biodistribution results indicated significantly greater tumor uptake of radiolabeled peptides at 3 h after injection when pretargeting was performed with bsPAM4 as compared with the bispecific rituximab [20.2 +/- 5.5 percentage of injected dose per gram of tissue (%ID/g) versus 0.9 +/- 0.1%ID/g, respectively, for (111)In-IMP-156, and 16.8 +/- 4.8%ID/g versus 1.1 +/- 0.2%ID/g, respectively, for (99m)Tc-IMP-192]. Similar results were obtained at the 24-h time point. Tumor:nontumor ratios were >30 for all of the tissues except the kidneys, where a ratio of 7.8 +/- 2.8 was observed. By immunoscintigraphy, tumors could be visualized as early as 30 min after injection of the radiolabeled peptide.

CONCLUSIONS

These studies demonstrate the feasibility of using the pretargeted, bispecific antibody technology for nuclear imaging of pancreatic cancer. The advantage of pretargeted bsPAM4 antibody as an imaging platform is the high specificity for pancreatic cancer as compared with the physicochemical parameters identified by current imaging technologies.