Pancreatic perfusion: noninvasive quantitative assessment with dynamic contrast-enhanced MR imaging without and with secretin stimulation in healthy volunteers--initial results

Arterial Spin Labeling (ASL) MRI in Evaluating Pancreatic Blood Perfusion in Subjects With Different Glucose Tolerances

BACKGROUND

The pancreas plays a central role in type 2 diabetes mellitus (T2DM), and its blood flow is usually associated with insulin release demand.

PURPOSE

To noninvasively assess pancreatic blood flow (PBF) changes and modulation in people with different glucose tolerance following a glucose challenge using ASL MRI.

STUDY TYPE

Prospective.

SUBJECTS

Fourteen prediabetes, 22 T2DM, and 40 normal.

FIELD STRENGTH/SEQUENCE

Pseudo-continuous ASL with a turbo gradient spin echo sequence at 3.0 T.

ASSESSMENT

All normal and subjects (diagnosed by oral glucose tolerance test) underwent ASL after fasting for at least 6 hours. The normal and prediabetes groups additionally had ASL scans at 5, 10, 15, 20, and 25 minutes following oral glucose (50 mL, 5%). PBF maps were generated from the ASL data and measured at body and tail. The ability of baseline PBF (BL-PBF) of body, tail (BL-PBFtail), and their average to determine abnormal glucose tolerance and stage was assessed.

STATISTICAL TESTS

ANOVA, Mann-Whitney U test, Kruskal-Wallis H test, paired sample t-test, intra-class correlation coefficient, repeated measures ANOVA, correlation analysis, receiver operating characteristic analysis, and logistic regression analysis. A P value <0.05 was considered significant.

RESULTS

There were significant differences in BL-PBF among the three groups. The prediabetes group exhibited significantly lower PBF than the normal group at all time points; Both groups showed similar changing trends in PBF (peaking at the 15th minute and subsequently declining). The BL-PBFtail had the highest diagnostic performance when evaluating abnormal glucose tolerance or stage (area under the curves = 0.800, 0.584, respectively) and was an independent risk factor for glucose tolerance status.

DATA CONCLUSION

ASL can noninvasively assess changes in PBF among individuals with varying glucose tolerance and in response to glucose challenge, which could be linked to insulin release demand and might help characterize changes in pancreatic endocrine function.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 1.

Visceral Fat Accumulation Is Related to Impaired Pancreatic Blood Perfusion and Beta-Cell Dysfunction in Obese Women

AIMS/HYPOTHESIS

Beta-cell failure plays a fundamental role in type 2 diabetes mellitus (T2DM) development. It has been shown that the beta-cells are among the most sensitive to hypoxia. We aimed to analyze whether decrease in pancreatic perfusion relates to 1/decline in beta-cell function and 2/visceral fat accumulation in patients with T2DM.

METHODS

Fifteen women with T2DM on metformin therapy alone and fifteen women of comparable age and BMI without prediabetes/diabetes were cross-sectionally examined: clinical and anthropometric examination, fast sampled intravenous glucose tolerance test (FSIVGTT), dynamic contrast-enhanced magnetic resonance imaging to assess pancreatic perfusion (area under the curve of postcontrast saturation, AUCTSIC), and visceral adiposity (VAT, calculated from transverse sections at the level L2-L5 vertebrae).

RESULTS

Pancreatic blood perfusion (AUCTSIC) did not differ between groups (p = 0.273), but it negatively correlated with BMI (r = -0.434, p = 0.017), WHR (r = -0.411, p = 0.024), and VAT (r = -0.436, p = 0.016) in both groups. Moreover, AUCTSIC in the head of the pancreas negatively correlated with the level of fasting glycemia (r = -0.401, p = 0.028) and HOMA-IR (r = -0.376, p = 0.041).

DISCUSSION/CONCLUSION

We showed that decreased pancreatic perfusion did not relate to beta-cell dysfunction in early stages of T2DM development, but it was related to VAT, insulin resistance, and higher fasting glycemia. Furthermore, lower pancreatic perfusion was related to VAT, insulin resistance, and higher fasting glycemia.

Quantitative Magnetic Resonance Imaging of the Pancreas of Individuals With Diabetes

Magnetic resonance imaging (MRI) has the potential to improve our understanding of diabetes and improve both diagnosis and monitoring of the disease. Although the spatial resolution of MRI is insufficient to directly image the endocrine pancreas in people, the increasing awareness that the exocrine pancreas is also involved in diabetes pathogenesis has spurred new MRI applications. These techniques build upon studies of exocrine pancreatic diseases, for which MRI has already developed into a routine clinical tool for diagnosis and monitoring of pancreatic cancer and pancreatitis. By adjusting the imaging contrast and carefully controlling image acquisition and processing, MRI can quantify a variety of tissue pathologies. This review introduces a number of quantitative MRI techniques that have been applied to study the diabetic pancreas, summarizes progress in validating and standardizing each technique, and discusses the need for image analyses that account for spatial heterogeneity in the pancreas.

Can Disturbed Liver Perfusion Revealed in p-CT on the First Day of Acute Pancreatitis Provide Information about the Expected Severity of the Disease?

Background

The aim of the study was to evaluate the prognostic properties of perfusion parameters of liver parenchyma based on computed tomography (CT) of patients with acute pancreatitis (AP) made on the first day of onset of symptoms, to assess their usefulness in identifying patients with increased risk of the development of severe AP.

Methods

79 patients with clinical symptoms and biochemical criteria indicative of AP underwent perfusion computed tomography (p-CT) within 24 hours after onset of the symptoms. Perfusion parameters in 41 people who developed a severe form of AP were compared with parameters in 38 patients in whom the course of AP was mild.

Results

Statistical differences in the liver perfusion parameters between the group of patients with mild and severe AP were shown. The permeability-surface area product was significantly lower, and the hepatic arterial fraction was significantly higher in the group of patients with progression of AP.

Conclusions

Based on the results, it seems that p-CT performed on the first day from the onset of AP is a method that, by revealing disturbances in hepatic perfusion, can help in identifying patients with increased risk of the development of severe AP.

Pancreatic perfusion modulation following glucose stimulation assessed by noninvasive arterial spin labeling (ASL) MRI

BACKGROUND

More than 100 million adults in the US suffer from prediabetes or type-2 diabetes. Noninvasive imaging of pancreas endocrine function might provide a surrogate marker of β-cell functional integrity loss linked to this disease.

PURPOSE

To noninvasively assess pancreatic blood-flow modulation following a glucose challenge using arterial spin labeling (ASL) MRI.

STUDY TYPE

Prospective.

SUBJECTS

Fourteen adults (30 ± 7 years old, 3M/11F, body mass index [BMI] = 24 ± 3 kg.m^-2 ).

FIELD STRENGTH/SEQUENCE

3T MRI / background-suppressed pseudocontinuous PCASL preparation with single-shot fast-spin-echo (FSE) readout before and after an oral glucose challenge using either fruit juice (n = 7) or over-the-counter glucose gel (n = 7).

ASSESSMENT

Subjects were fasting prior to initiation of oral stimulation, then dynamic perfusion measurements were performed every 2 minutes for 30 minutes. We quantified absolute blood flow at each timepoint.

STATISTICAL TESTS

Repeated-measures analysis of variance (ANOVA) followed by paired t-tests to assess for a significant effect of glucose challenge on measured perfusion.

RESULTS

Measured basal blood flow was 187 ± 53 mL/100g/min. A significant blood flow increase of +38 ± 26% was observed 10 minutes poststimulation (P < 0.05) and continuing until the end of the experiment. The gel stimulation provided the most consistent results, with an early rise followed by an additional later increase consistent with the known pancreatic insulin response to elevated blood glucose. Across-subject variations in blood flow increase were partially attributable to basal flow, with a negative correlation of r = -0.84 between basal and maximal relative flow increase in the gel group.

DATA CONCLUSION

ASL can be used to measure pancreatic flow in response to a glucose challenge, which could be linked to insulin release and secretion. This paradigm might be useful to characterize disorders of glucose regulation.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2020;51:854-860.

Quantitative pancreatic MRI: a pathology-based review

MRI plays an important role in the clinical management of pancreatic disorders and interpretation is reliant on qualitative assessment of anatomy. Conventional sequences capturing pancreatic structure can however be adapted to yield quantitative measures which provide more diagnostic information, with a view to increasing diagnostic accuracy, improving patient stratification, providing robust non-invasive outcome measures for therapeutic trials and ultimately personalizing patient care. In this review, we evaluate the use of established techniques such as secretin-enhanced MR cholangiopancreatography, diffusion-weighted imaging, T ₁, T ₂* and fat fraction mapping, but also more experimental methods such as MR elastography and arterial spin labelling, and their application to the assessment of diffuse pancreatic disease (including chronic, acute and autoimmune pancreatitis/IgG4 disease, metabolic disease and iron deposition disorders) and cystic/solid focal pancreatic masses. Finally, we explore some of the broader challenges to their implementation and future directions in this promising area.

Intra- and interobserver reproducibility of pancreatic perfusion by computed tomography

The aim of this study was to measure intra- and interobserver agreement among radiologists in the assessment of pancreatic perfusion by computed tomography (CT). Thirty-nine perfusion CT scans were analyzed. The following parameters were measured by three readers: blood flow (BF), blood volume (BV), mean transit time (MTT) and time to peak (TTP). Statistical analysis was performed using the Bland-Altman method, linear mixed model analysis, and intraclass correlation coefficient (ICC). There was no significant intraobserver variability for the readers regarding BF, BV or TTP. There were session effects for BF in the pancreatic body and MTT in the pancreatic tail and whole pancreas. There were reader effects for BV in the pancreatic head, pancreatic body and whole pancreas. There were no effects for the interaction between session and reader for any perfusion parameter. ICCs showed substantial agreement for the interobserver measurements and moderate to substantial agreement for the intraobserver measurements, with the exception of MTT. In conclusion, satisfactory reproducibility of measurements was observed for TTP in all pancreatic regions, for BF in the head and BV in the tail, and these parameters seem to ensure a reasonable estimation of pancreatic perfusion.

Borderline resectable pancreatic cancer: conceptual evolution and current approach to image-based classification

Background

Diagnostic imaging plays a critical role in the initial diagnosis and therapeutic monitoring of pancreatic adenocarcinoma. Over the past decade, the concept of 'borderline resectable' pancreatic cancer has emerged to describe a distinct subset of patients existing along the spectrum from resectable to locally advanced disease for whom a microscopically margin-positive (R1) resection is considered relatively more likely, primarily due to the relationship of the primary tumor with surrounding vasculature.

Materials and methods

This review traces the conceptual evolution of borderline resectability from a radiological perspective, including the debates over the key imaging criteria that define the thresholds between resectable, borderline resectable, and locally advanced or metastatic disease. This review also addresses the data supporting neoadjuvant therapy in this population and discusses current imaging practices before and during treatment.

Results

A growing body of evidence suggests that the borderline resectable group of patients may particularly benefit from neoadjuvant therapy to increase the likelihood of an ultimately margin-negative (R0) resection. Unfortunately, anatomic and imaging criteria to define borderline resectability are not yet universally agreed upon, with several classification systems proposed in the literature and considerable variance in institution-by-institution practice. As a result of this lack of consensus, as well as overall small patient numbers and lack of established clinical trials dedicated to borderline resectable patients, accurate evidence-based diagnostic categorization and treatment selection for this subset of patients remains a significant challenge.

Conclusions

Clinicians and radiologists alike should be cognizant of evolving imaging criteria for borderline resectability given their profound implications for treatment strategy, follow-up recommendations, and prognosis.

Contrast-enhanced ultrasonography of the pancreas shows impaired perfusion in pancreas insufficient cystic fibrosis patients

Background

Perfusion assessment of the pancreas is challenging and poorly evaluated. Pancreatic affection is a prevalent feature of cystic fibrosis (CF). Little is known about pancreatic perfusion in CF. We aimed to assess pancreatic perfusion by contrast-enhanced ultrasound (CEUS) analysed in the bolus-and-burst model and software.

Methods

We performed contrast enhanced ultrasound of the pancreas in 25 CF patients and 20 healthy controls. Perfusion data was analysed using a dedicated perfusion model providing the mean capillary transit-time (MTT), blood flow (BF) and blood-volume (BV). CF patients were divided according to exocrine function.

Results

The pancreas insufficient CF patients had longer MTT (p ≤ 0.002), lower BF (p < 0.001) and lower BV (p < 0.05) compared to the healthy controls and sufficient CF patients. Interrater analysis showed substantial agreement for the analysis of mean transit time.

Conclusion

The bolus-and-burst method used on pancreatic CEUS-examinations demonstrates reduced perfusion in CF patients with pancreas affection. The perfusion model and software requires further optimization and standardization to be clinical applicable for the assessment of pancreatic perfusion.

Electronic supplementary material

The online version of this article (10.1186/s12880-018-0259-3) contains supplementary material, which is available to authorized users.

Repeatability and correlations of dynamic contrast enhanced and T2* MRI in patients with advanced pancreatic ductal adenocarcinoma

BACKGROUND

In current oncological practice of pancreatic ductal adenocarcinoma (PDAC), there is a great demand for response predictors and markers for early treatment evaluation. In this study, we investigated the repeatability and the interaction of dynamic contrast enhanced (DCE) and T2* MRI in patients with advanced PDAC to enable for such evaluation using these techniques.

MATERIALS & METHODS

15 PDAC patients underwent two DCE, T2* and anatomical 3 T MRI sessions before start of treatment. Parametric maps were calculated for the transfer constant (K^trans), rate constant (k_ep), extracellular extravascular space (v_e) and perfusion fraction (v_p). Quantitative R2* (1/T2*) maps were obtained from the multi-echo T2* images. Differences between normal and cancerous pancreas were determined using a Wilcoxon matched pairs test. Repeatability was obtained using Bland-Altman analysis and relations between DCE and T2*/R2* were observed by Spearman correlation and voxel-wise binned plots of tumor voxels.

RESULTS

PDAC K^trans (p = 0.007), k_ep (p < 0.001), v_p (p = 0.035) were lower and v_e (p < 0.001) was higher compared to normal pancreas. The coefficient of variation between sessions was 21.8% for K^trans, 9.9% for k_ep, 19.3% for v_e, 18.2% for v_p and 18.7% for R2*. Variation between patients ranged from 20.2% for k_ep to 43.6% for K^trans. In the tumor both K^trans (r = 0.56, p = 0.030) and v_e (r = 0.54, p = 0.037) showed a positive correlation with T2*. Voxel wise analysis showed a steep increase in R2* for tumor voxels with lower K^trans and v_e.

CONCLUSION

We showed good repeatability of DCE and T2* related MRI parameters in advanced PDAC patients. Furthermore, we have illustrated the relation of DCE K^trans and v_e with tissue T2* and R2* indicating substantial value of these parameters for detecting tumor hypoxia in future studies. The results from our study pave the way for further response evaluation studies and patient selection based on DCE and T2* parameters.

Dynamic non-invasive ASL perfusion imaging of a normal pancreas with secretin augmented MR imaging

OBJECTIVES

To investigate prospectively the repeatability of pancreatic perfusion measurements using arterial spin labelling (ASL) and to determine the increase in perfusion due to secretin stimulation.

MATERIAL AND METHODS

An (FAIR)-TrueFISP ASL sequence was applied to determine the perfusion of the pancreatic head in a 3T MRI scanner. Ten healthy volunteers (four men, six women: mean age 28.5 ± 4.6 years; age range 25-40 years) were investigated twice within 1 week. The inter-individual variability was calculated using the standard deviation. Intra-individual agreement between the first and second scan was estimated using the Pearson correlation coefficient. A paired Wilcoxon rank-sum test was used to compare perfusion at baseline (BL) and during secretin stimulation.

RESULTS

The mean BL perfusion of the pancreatic head was 285 ± 96 mL/100 g/min with an intra-individual correlation coefficient of 0.67 (strong) for repeated measurements. Secretin stimulation led to a significant increase (by 81%) in perfusion of the pancreatic head to 486 ±156 mL/100 g/min (p=0.002) with an intra-individual correlation of 0.29 (weak). A return to BL values was observed after 239 ± 92 s with a moderate intra-individual correlation coefficient of 0.42 for repeat measurements.

CONCLUSION

Dynamic non-invasive ASL imaging of the pancreas permitted quantification of pancreatic perfusion in a clinically applicable setting.

KEY POINTS

• ASL imaging of the pancreas permitted quantification of pancreatic perfusion • Secretin stimulation led to a significant increase in pancreatic perfusion • The intra-individual correlation coefficient for baseline perfusion was strong for repeated measurements.

The application of high-field magnetic resonance perfusion imaging in the diagnosis of pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer death in the world. It is a disease of insidious progression and high lethality. The present study was to investigate the diagnostic value of high-filed magnetic resonance (MR) perfusion imaging in pancreatic cancer. Thirty-three patients with suspected pancreatic cancer were recruited in our study and underwent routine MR imaging. When compared with para-tumoral and normal tissue, the pancreatic lesions showed significant lower slope, peak enhancement (PE), and signal enhancement ratio (SER) as well as higher time to peak (TTP). Para-tumoral tissue was found to have significantly lower slope and PE, slightly higher TTP than normal tissue. MR perfusion imaging displays hemodynamic alterations in both pancreatic cancer and surrounding pancreatic tissue, and provides indirect assessment of tumor vascularity. In conclusion, high field MR perfusion imaging has important clinical significance in early diagnosis of pancreatic cancer.

Modifications of pancreatic diffusion MRI by tissue characteristics: what are we weighting for?

Diffusion-weighted imaging holds the potential to improve the diagnosis and biological characterization of pancreatic disease, and in particular pancreatic cancer, which exhibits decreased values of the apparent diffusion coefficient (ADC). Yet, variable and overlapping ADC values have been reported for the healthy and the pathological pancreas, including for cancer and other benign conditions. This controversy reflects the complexity of probing the water-diffusion process in the pancreas, which is dependent upon multiple biological factors within this organ's unique physiological environment. In recent years, extensive studies have investigated the correlation between tissue properties including cellularity, vascularity, fibrosis, secretion and microstructure and pancreatic diffusivity. Understanding how the various physiological and pathological features and the underlying functional processes affect the diffusion measurement may serve to optimize the method for improved diagnostic gain. Therefore, the aim of the present review article is to elucidate the relationship between pancreatic tissue characteristics and diffusion MRI measurement.

Functional MRI of human pancreas using BOLD contrast: Responses following glucose ingestion

PURPOSE

To evaluate the response of the pancreas to glucose ingestion in healthy volunteers by blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI).

MATERIALS AND METHODS

This study was approved by the local Ethics Committee, and informed consent was obtained from all subjects. A multiple gradient recalled echo (mGRE) sequence was performed on a 3.0T MR scanner in 12 healthy volunteers before and after glucose or water ingestion. Pancreatic T2* values were calculated from it at each timepoint, and changes following stimulation were analyzed using summary measures. The valley values and times were compared between the glucose and water ingestion by paired samples t-test. The repeatability of the pancreatic T2* measurements was assessed by calculating the intraclass correlation coefficient (ICC) and coefficient of variation (CV).

RESULTS

Pancreatic T2* measurements showed good repeatability (all ICC >0.75). CV for the six baseline acquisitions was 2.74 ± 0.97%, indicating a 5.37% measurement error. A transient but significant decrease (-6.88 ± 1.01%, P value, 0.0005-0.0467) in the pancreatic T2* values was observed within 5 minutes after glucose ingestion, rather than water consumption. Compared to water, glucose ingestion induced earlier (valley times: 3.46 ± 3.22 vs. 7.75 ± 4.09 min, P = 0.0006) and remarkable pancreatic T2* decrease (valley values: -15.33 ± 5.90% vs. -6.88 ± 3.11%, P = 0.0006).

CONCLUSION

BOLD MRI enabled noninvasive quantification of pancreatic T2* changes during glucose stimulation. Glucose ingestion resulted in a rapid and significant pancreatic T2* decrease in healthy young volunteers.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 2 J. MAGN. RESON. IMAGING 2017;46:831-836.

Secretin-Stimulated Magnetic Resonance Imaging Assessment of the Benign Pancreatic Disorders: Systematic Review and Proposal for a Standardized Protocol

This systemic review summarizes the current literature and general consensus on secretin-stimulated magnetic resonance imaging (s-MRI) of the benign pancreatic disorders and discusses important aspects on how s-MRI is optimally performed. The aim is to provide an overview, for clinicians and radiologist, of the s-MRI protocols and the range of clinical applications. Furthermore, the review will summarize the criteria for evaluation of pancreatic morphology and function based on s-MRI.The literature search indentified 69 original articles and 15 reviews. Chronic pancreatitis was the disease that was most frequently assessed by s-MRI (33%), followed by acute pancreatitis (9%). Dynamic thick-slab 2-dimensional magnetic resonance cholangiopancreatography was the most used imaging sequence (86%). The diameter of the main pancreatic duct (75%) and pancreatic exocrine function based on visual grading of duodenal filling (67%) were the most evaluated pancreatic features. Sufficient similarities between studies were identified to propose the most agreeable standardized s-MRI protocol for morphological and functional assessment of the pancreas. In the future, more research and increased collaboration between centers is necessary to achieve more consensus and optimization of s-MRI protocols.

Survival of encapsulated islets: More than a membrane story

At present, proven clinical treatments but no cures are available for diabetes, a global epidemic with a huge economic burden. Transplantation of islets of Langerhans by their infusion into vascularized organs is an experimental clinical protocol, the first approach to attain cure. However, it is associated with lifelong use of immunosuppressants. To overcome the need for immunosuppression, islets are encapsulated and separated from the host immune system by a permselective membrane. The lead material for this application is alginate which was tested in many animal models and a few clinical trials. This review discusses all aspects related to the function of transplanted encapsulated islets such as the basic requirements from a permselective membrane (e.g., allowable hydrodynamic radii, implications of the thickness of the membrane and relative electrical charge). Another aspect involves adequate oxygen supply, which is essential for survival/performance of transplanted islets, especially when using large retrievable macro-capsules implanted in poorly oxygenated sites like the subcutis. Notably, islets can survive under low oxygen tension and are physiologically active at > 40 Torr. Surprisingly, when densely crowded, islets are fully functional under hyperoxic pressure of up to 500 Torr (> 300% of atmospheric oxygen tension). The review also addresses an additional category of requirements for optimal performance of transplanted islets, named auxiliary technologies. These include control of inflammation, apoptosis, angiogenesis, and the intra-capsular environment. The review highlights that curing diabetes with a functional bio-artificial pancreas requires optimizing all of these aspects, and that significant advances have already been made in many of them.

Perfusion-CT--Can We Predict Acute Pancreatitis Outcome within the First 24 Hours from the Onset of Symptoms?

PURPOSE

Severe acute pancreatitis (AP) is still a significant clinical problem which is associated with a highly mortality. The aim of this study was the evaluation of prognostic value of CT regional perfusion measurement performed on the first day of onset of symptoms of AP, in assessing the risk of developing severe form of acute pancreatitis.

MATERIAL AND METHODS

79 patients with clinical symptoms and biochemical criteria indicative of acute pancreatitis (acute upper abdominal pain, elevated levels of serum amylase and lipase) underwent perfusion CT within 24 hours after onset of symptoms. The follow-up examinations were performed after 4-6 days to detect progression of the disease. Perfusion parameters were compared in 41 people who developed severe form of AP (pancreatic and/or peripancreatic tissue necrosis) with parameters in 38 consecutive patients in whom course of AP was mild. Blood flow, blood volume, mean transit time and permeability surface area product were calculated in the three anatomic pancreatic subdivisions (head, body and tail). At the same time the patient's clinical status was assessed by APACHE II score and laboratory parameters such as CRP, serum lipase and amylase, AST, ALT, GGT, ALP and bilirubin were compared.

RESULTS

Statistical differences in the perfusion parameters between the group of patients with mild and severe AP were shown. Blood flow, blood volume and mean transit time were significantly lower and permeability surface area product was significantly higher in patients who develop severe acute pancreatitis and presence of pancreatic and/or peripancreatic necrosis due to pancreatic ischemia. There were no statistically significant differences between the two groups in terms of evaluated on admission severity of pancreatitis assessed using APACHE II score and laboratory tests.

CONCLUSIONS

CT perfusion is a very useful indicator for prediction and selection patients in early stages of acute pancreatitis who are at risk of developing pancreatic and/or peripancreatic necrosis already on the first day of the onset of symptoms and can be used for treatment planning and monitoring of therapy of acute pancreatitis. Early suspicion of possible pancreatic necrosis both on the basis of scores based on clinical status and laboratory tests have low predictive value.

Personalized medicine in pancreatic cancer: the revolution has begun

Pancreatic ductal adenocarcinoma carries a dismal prognosis. Both chemotherapy and targeted therapies have been disappointing when administered to unselected populations. Recently, progress has been made in our understanding of the genomic landscape of this cancer which displays remarkable heterogeneity suggesting a reorientation of management and research strategies based on molecular characterization and adapted personalized therapy. Resectable disease offers new opportunities for translational research through functional imaging response evaluation and tumor tissue acquisition before and after neoadjuvant therapy. There is urgent need for clinical trials based on molecular profiling in pancreatic ductal adenocarcinoma. In this review we discuss opportunities and limitations of these new strategies, underlining the importance of tissue acquisition and integration of molecular biomarkers in future molecularly driven clinical trials.

Temporal assessment of pancreatic blood flow and perfusion following secretin stimulation using noninvasive MRI

PURPOSE

To dynamically quantify pancreatic perfusion and flow within the arteries supplying the pancreas in response to secretin stimulation.

MATERIALS AND METHODS

Twelve healthy male subjects were scanned at 1.5T with arterial spin labeling to measure tissue perfusion and phase contrast magnetic resonance imaging (MRI) to measure vessel flow. Superior mesenteric (SMA), gastroduodenal (GDA), common hepatic (HA), and splenic (SA) arterial flow and pancreatic perfusion were serially measured for 50 minutes following 1 IU/kg intravenous secretin. The significance of differences between timepoints was tested using a repeated measures one-way analysis of variance (ANOVA).

RESULTS

Baseline blood flow (mean ± SEM or median [IQR]) for SMA, HA, SA, and GDA was 7.6 ± 1.3, 4.0 ± 0.5, 8.2 ± 0.8, and 0.9 (0.8-1.4) ml/s, respectively. Baseline pancreatic perfusion was 200 ± 25 ml/100g/min. Blood flow increased in the SMA (234%, P < 0.0001) and GDA (155%, P = 0.015) immediately after secretin injection. Reduced HA blood flow was observed after 10 minutes (P = 0.066) with no change in SA flow (P = 0.533). Increased pancreatic perfusion was maintained for 40 minutes after injection with a maximal increase at 5 minutes (16.8%, P = 0.025).

CONCLUSION

Intravenous secretin resulted in significant temporal changes in pancreatic perfusion and arterial blood flow.

New challenges in perioperative management of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death in the industrialized world. Despite progress in the understanding of the molecular and genetic basis of this disease, the 5-year survival rate has remained low and usually does not exceed 5%. Only 20%-25% of patients present with potentially resectable disease and surgery represents the only chance for a cure. After decades of gemcitabine hegemony and limited therapeutic options, more active chemotherapies are emerging in advanced PDAC, like 5-Fluorouracil, folinic acid, irinotecan and oxaliplatin and nab-paclitaxel plus gemcitabine, that have profoundly impacted therapeutic possibilities. PDAC is considered a systemic disease because of the high rate of relapse after curative surgery in patients with resectable disease at diagnosis. Neoadjuvant strategies in resectable, borderline resectable, or locally advanced pancreatic cancer may improve outcomes. Incorporation of tissue biomarker testing and imaging techniques into preoperative strategies should allow clinicians to identify patients who may ultimately achieve curative benefit from surgery. This review summarizes current knowledge of adjuvant and neoadjuvant treatment for PDAC and discusses the rationale for moving from adjuvant to preoperative and perioperative therapeutic strategies in the current era of more active chemotherapies and personalized medicine. We also discuss the integration of good specimen collection, tissue biomarkers, and imaging tools into newly designed preoperative and perioperative strategies.

Contrast enhanced ultrasound with quantitative perfusion analysis for objective characterization of pancreatic ductal adenocarcinoma: A feasibility study

The aim of this study was to determine whether contrast enhanced ultrasound (CEUS) quantitative perfusion analysis allows an objective characterization of ductal adenocarcinoma (ADK) of the pancreas. Patients with pancreatic ADK underwent CEUS. All examinations were performed on an Acuson S2000 system (Siemens, Erlangen, Germany) after the iv administration of 2.4 mL contrast agent (SonoVue^®, Bracco, Milan, Italy). All lesions were pathologically proved. An operator manually drew different regions of interest within the tumor and the adjacent parenchyma to allow the quantitative perfusion analysis. The mean values of peak of enhancement, time to peak and ascending curve were calculated and compared using the Student’s t test. The quantitative perfusion analysis was possible in all lesions. The mean values of the peak of enhancement, time to peak and ascending curve were 17.19%, 7.97 s and 159.52% s within the tumor and 33.57%, 8.89 s and 355.29% s within the adjacent parenchyma. The peak of enhancement and the ascending curve values were significantly different within the tumor and the adjacent parenchyma. Thus, CEUS allows the quantitative perfusion analysis of pancreatic ductal adenocarcinoma.

Empirical mathematical model for dynamic manganese-enhanced MRI of the murine pancreas for assessment of β-cell function

Autoimmune ablation of pancreatic β-cells and alteration of its microvasculature may be a predictor of Type I diabetes development. A dynamic manganese-enhanced MRI (MEMRI) approach and an empirical mathematical model were developed to monitor whole pancreatic β-cell function and vasculature modifications in mice. Normal and streptozotocin-induced diabetic FVB/N mice were imaged on a 9.4T MRI system using a 3D magnetization prepared rapid acquisition gradient echo pulse sequence to characterize low dose manganese kinetics in the pancreas head, body and tail. Average signal enhancement in the pancreas (head, body, and tail) as a function of time was fit by a novel empirical mathematical model characterizing contrast uptake/washout rates and yielding parameters describing peak signal, initial slope, and initial area under the curve. Signal enhancement from glucose-induced manganese uptake was fit by a linear function. The results demonstrated that the diabetic pancreatic tail had a significantly lower contrast uptake rate, smaller initial slope/initial area under the curve, and a smaller rate of Mn uptake following glucose activation (p<0.05) compared to the normal pancreatic tail. These observations parallel known patterns of β-cell loss and alteration in supportive vasculature associated with diabetes. Dynamic MEMRI is a promising technique for assessing β-cell functionality and vascular perfusion with potential applications for monitoring diabetes progression and/or therapy.

Evaluation of pancreatic cancer by multiple breath-hold dynamic contrast-enhanced magnetic resonance imaging at 3.0T

OBJECTIVE

To investigate the microcirculation in pancreatic cancer by pharmacokinetic analysis of multiple breath-hold dynamic contrast-enhanced magnetic resonance imaging at 3.0T.

MATERIALS AND METHODS

Multiple breath-hold dynamic contrast-enhanced magnetic resonance imaging was performed in 40 healthy volunteers and 40 patients with pancreatic cancer proven by histopathology using an axial three-dimensions fat-saturated T1-weighted spoiled-gradient echo sequence at 3.0T. A two compartment model with T1 correction was used to quantify the transfer constant, the rate constant of backflux from the extravascular extracellular space to the plasma and the extravascular extracellular space fractional volume in pancreatic cancer, obstructive pancreatitis distal to the malignant tumor, adjacent pancreatic tissue proximal to the tumor and normal pancreas. All parameters were statistically analyzed.

RESULTS

Statistical differences were noticed in both the transfer constant (p=0.000075) and the rate constant of backflux (p=0.006) among different tissues. Both the transfer constant and the rate constant of backflux in pancreatic cancer were statistically lower than those in normal pancreas and adjacent pancreatic tissue (p<0.05). Both the transfer constant and the rate constant of backflux in obstructive pancreatitis were statistically lower than those in normal pancreas and adjacent pancreatic tissue (p<0.05). The extravascular extracellular space fractional volume in pancreatic cancer was statistically lager than that in normal pancreas (p=0.002).

CONCLUSION

Multiple breath-hold dynamic contrast-enhanced magnetic resonance imaging offers a useful technique to evaluate the microenvironment in pancreatic cancer at 3.0T. Compared to normal pancreas, pancreatic cancer has lower transfer constant, rate constant of backflux and larger extravascular extracellular space fractional volume.

Xenon-inhalation computed tomography for noninvasive quantitative measurement of tissue blood flow in pancreatic tumor

BACKGROUND AND AIMS

The purpose of this prospective study was to demonstrate the ability to measure pancreatic tumor tissue blood flow (TBF) with a noninvasive method using xenon inhalation computed tomography (xenon-CT) and to correlate TBF with histological features, particularly microvascular density (MVD).

METHODS

TBFs of pancreatic tumors in 14 consecutive patients were measured by means of xenon-CT at diagnosis and following therapy. Serial abdominal CT scans were obtained before and after inhalation of nonradioactive xenon gas. TBF was calculated using the Fick principle. Furthermore, intratumoral microvessels were stained with anti-CD34 monoclonal antibodies before being quantified by light microscopy (×200). We evaluated MVD based on CD34 expression and correlated it with TBF.

RESULTS

The quantitative TBF of pancreatic tumors measured by xenon CT ranged from 22.3 to 111.4 ml/min/100 g (mean ± SD, 59.6 ± 43.9 ml/min/100 g). High correlation (r = 0.885, P < 0.001) was observed between TBF and intratumoral MVD.

CONCLUSION

Xenon-CT is feasible in patients with pancreatic tumors and is able to accurately estimate MVD noninvasively.

New strategies and designs in pancreatic cancer research: consensus guidelines report from a European expert panel

Although the treatment of pancreatic ductal adenocarcinoma (PDAC) remains a huge challenge, it is entering a new era with the development of new strategies and trial designs. Because there is an increasing number of novel therapeutic agents and potential combinations available to test in patients with PDAC, the identification of robust prognostic and predictive markers and of new targets and relevant pathways is a top priority as well as the design of adequate trials incorporating molecular-driven hypothesis. We presently report a consensus strategy for research in pancreatic cancer that was developed by a multidisciplinary panel of experts from different European institutions and collaborative groups involved in pancreatic cancer. The expert panel embraces the concept of exploratory early proof of concept studies, based on the prediction of response to novel agents and combinations, and randomised phase II studies permitting the selection of the best therapeutic approach to go forward into phase III, where the recommended primary end point remains overall survival. Trials should contain as many translational components as possible, relying on standardised tissue and blood processing and robust biobanking, and including dynamic imaging. Attention should not only be paid to the pancreatic cancer cells but also to microenvironmental factors and stem/stellate cells.

Variability of CT contrast enhancement in the pancreas: a cause for concern?

BACKGROUND

Multidetector CT is a valuable technique for diagnosis/staging in several pancreatic pathologies. Diagnosis is usually based on tissue density measurements. Recently, newer functional CT techniques have been introduced. The aim of this study was to assess variability in perfusion and dual-energy CT data, and to compare these data with density measurements in the pancreas of a healthy population.

METHODS

Two groups were included: 20 patients underwent perfusion CT imaging, and 10 patients were scanned using a dual-energy protocol. In both groups, tissue density [Hounsfield units (HU)] was measured in the pancreatic head, body and tail. Functional data were calculated (blood flow/blood volume in the perfusion CT group, iodine concentration in the dual-energy group), and variability was assessed.

RESULTS

Density measurements were comparable for the perfusion and dual-energy CT groups, and ranged from 14 to 60 HU. Maximal enhancement differences between the head/body/tail of the pancreas ranged between 2 and 21 HU. Considerable variability was observed, both in density measurements (ranging from 3 to 34%) and in functional parameters (mean variability in perfusion CT parameters blood flow and blood volume was 21.3 and 10% respectively; mean variability in dual-energy iodine-mapping results was 24.4%).

CONCLUSION

This study demonstrated the presence of important intraindividual variability in pancreatic tissue contrast enhancement, regardless of the CT technique used. Considering the variability observed in this study, the use of cut-off values to characterize pancreatic pathologies seems troublesome, and morphologic primary and secondary changes will remain important, even when using novel functional imaging techniques. and IAP.

The metabolic features of normal pancreas and pancreatic adenocarcinoma: preliminary result of in vivo proton magnetic resonance spectroscopy at 3.0 T

OBJECTIVE

The objective of the study was to analyze the metabolic features and distribution of normal pancreas and pancreatic adenocarcinoma while determining the biomarker of pancreatic cancerous process.

METHODS

Twenty-seven control and 29 pancreatic adenocarcinoma patients underwent breath-hold 3-T proton magnetic resonance spectroscopy. The ratios of lipid (lipid/InW), choline-containing compounds (CCCs/InW), and fatty acids (FAs/InW) to nonsaturated internal water (InW) of the normal pancreas head and body-tail region, with cancerous and noncancerous regions in pancreatic adenocarcinoma, were calculated.

RESULTS

In normal pancreas, there were no statistical difference in the ratios of FAs to InW and lipid to InW of different regions, but CCCs/InW of body-tail area was greater than that of head (7.28 × 10⁻⁴ vs 3.23 × 10⁻⁴). In pancreatic cancer, FAs/InW and lipid/InW between cancerous and noncancerous region were different (3.44 × 10⁻⁴ vs 16.3 × 10⁻⁴ and 7.78 × 10⁻⁴ vs 36.3 × 10⁻⁴, respectively). Choline-containing compounds/InW in cancerous region was smaller than that in noncancerous region of pancreatic head cancer (1.62 × 10⁻⁴ vs 5.69 × 10⁻⁴) but similar to such region in body-tail cancer. Lipid/InW dropped in noncancerous regions (from 0.67 to 0.36), whereas there were no differences in FAs/InW and CCCs/InW between normal pancreas regions and noncancerous regions in pancreatic cancer.

CONCLUSIONS

In normal pancreas, CCCs of body-tail region was greater than that of head. Whereas in pancreatic adenocarcinoma, CCCs, FAs, and lipid were all decreased in cancerous region, lipid in the noncancerous region was also decreased compared with normal pancreas. Lipid may be the potential sensitive biomarker for pancreatic cancer.

Tumoral and nontumoral pancreas: correlation between quantitative dynamic contrast-enhanced MR imaging and histopathologic parameters

PURPOSE

To prospectively determine whether dynamic contrast material-enhanced (DCE) magnetic resonance (MR) quantitative parameters correlate with fibrosis and microvascular density (MVD) in malignant and benign solid pancreatic focal lesions and nontumoral pancreatic tissue.

MATERIALS AND METHODS

The institutional review board approved the study; written informed consent was obtained. DCE MR was performed in 28 patients with surgically resectable focal pancreatic lesions. DCE MR quantitative parameters derived from one-compartment (OC) (transfer rate constant [K(trans)] and distribution fraction [ƒ]) and two-compartment (TC) (K(trans), tissue volume fraction occupied by extravascular extracellular space [v(i)], and tissue volume fraction occupied by vascular space [v(p)]) pharmacokinetic models were correlated with fibrosis content and MVD counts in focal lesions and nontumoral tissue (Spearman correlation coefficient [SCC]). Pharmacokinetic parameters were compared (Mann-Whitney test) between tumoral and nontumoral tissue. Diagnostic performance of DCE MR fibrosis detection was assessed (receiver operator characteristic curve analysis).

RESULTS

K(trans) OC and K(trans) TC were significantly lower in primary malignant tumors compared with benign lesions (P = .023) and nontumoral pancreatic tissue downstream (P < .001) and upstream (P = .006); ƒ and v(i) were significantly higher in primary malignant tumors compared with nontumoral pancreatic tissue downstream (P = .012 and .018, respectively). Fibrosis was correlated negatively with K(trans) OC (SCC, -0.600) and K(trans) TC (SCC, -0.564) and positively with ƒ (SCC, 0.514) and v(i) (SCC, 0.464), with P < .001 (all comparisons). MVD was positively correlated with ƒ (SCC, 0.355; P = .019) and v(i) (SCC, 0.297; P = .038) but not with K(trans) OC (SCC, -0.140; P = .33) and K(trans) TC (SCC, -0.194; P = .181). Sensitivity and specificity for fibrosis detection were 65% (24 of 37) and 83% (10 of 12) for K(trans) OC (cutoff value, 0.35 min(-1)) and 76% (28 of 37) and 83% (10 of 12) for K(trans) TC (cutoff value, 0.29 min(-1)), respectively.

CONCLUSION

Quantitative DCE MR parameters, derived from pharmacokinetic models in malignant and benign pancreatic solid lesions and nontumoral pancreatic tissue, were significantly correlated with fibrosis and MVD.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11103515/-/DC1.

Feasibility of measuring human pancreatic perfusion in vivo using imaging techniques

OBJECTIVE

The objective of this study was to demonstrate the feasibility of pancreatic perfusion computed tomography (CT) and review pancreatic perfusion measurements by various imaging modalities.

METHODS

Dynamic CT data from 8 patients (4 men; mean age, 64.8 [SD, 12.1] years; range, 40-80 years) with normal pancreas were analyzed using 2 analytical models: the maximum-slope and compartment-model methods. Literature search was also performed.

RESULTS

Although the perfusion value estimated by the maximum-slope method (88.1 [SD, 42.1] mL/min per 100 mL) was significantly smaller than that of the compartment-model method (127.0 [SD, 70.5]; P < 0.001), there was a linear correlation between them (r = 0.97, P < 0.001). In the literature review, 15 studies that reported the absolute values of normal pancreatic perfusion, by using perfusion CT, dynamic magnetic resonance imaging, hydrogen gas clearance method, and 15O-H2O-positron emission tomography were found. The reported mean values of normal pancreatic perfusion ranged from 38.4 to 356 mL/min per 100 mL, and there was a great deal of individual variation.

CONCLUSIONS

Perfusion CT may provide reliable perfusion measurements of the pancreas, and the normal value was estimated at around 100 mL/min per 100 mL with a great deal of individual variation. The maximum-slope method may provide a lower perfusion value compared with the compartment-model method.

64-slice CT perfusion imaging of pancreatic adenocarcinoma and mass-forming chronic pancreatitis

RATIONALE AND OBJECTIVES

To investigate 64 computed tomography (CT) perfusion imaging features of patients with pancreatic cancer and mass-forming chronic pancreatitis.

MATERIALS AND METHODS

Between January 2003 and April 2010, 234 patients with pancreatic mass underwent 64-CT perfusion imaging. Among them, the histopathological results of 64 patients were proven to be pancreatic adenocarcinoma and 15 patients were proven to be mass-forming chronic pancreatitis. Additionally, CT perfusion imaging was performed in 33 healthy volunteers served as controls. The slice data were processed using CT perfusion software. Perfusion parameters including time density curve, blood flow, blood volume, permeability, peak enhancement, and time to peak were recorded.

RESULTS

Blood flow was 77% lower in patients with pancreatic adenocarcinoma than in controls, 48% lower in patients with mass-forming chronic pancreatitis than in controls, and 56% lower in patients with pancreatic adenocarcinoma than with mass-forming chronic pancreatitis (P < .016). Blood volume was 65% lower in pancreatic adenocarcinoma than in controls, 27% lower in mass-forming chronic pancreatitis than in controls, and 53% lower in cancer than mass-forming chronic pancreatitis (P < .016). Permeability was 559% higher in pancreatic adenocarcinoma than in controls, 821% higher in mass-forming chronic pancreatitis than in controls, and 28% lower in cancer than mass-forming chronic pancreatitis (P < .016). Peak enhancement was 27% lower and time to peak 23% longer in pancreatic adenocarcinoma than mass-forming chronic pancreatitis (P < .016). Time-density curve showed the peak of mass-forming chronic pancreatitis is earlier and higher than that of pancreatic adenocarcinoma, and the peak of mass-forming chronic pancreatitis is later and lower than that of controls.

CONCLUSION

CT perfusion imaging can provide additional quantitative hemodynamic information of pancreatic adenocarcinoma and mass-forming chronic pancreatitis.

Differentiation of pancreas carcinoma from healthy pancreatic tissue using multiple b-values: comparison of apparent diffusion coefficient and intravoxel incoherent motion derived parameters

OBJECTIVES

To evaluate in detail the diagnostic performance of diffusion-weighted imaging (DWI) to differentiate pancreas carcinoma from healthy pancreas using the apparent diffusion coefficient (ADC) and parameters derived from the intravoxel incoherent motion (IVIM) theory.

MATERIALS AND METHODS

Twenty-three patients with pancreas carcinoma and 14 volunteers with healthy pancreas were examined at 1.5 Tesla using a single-shot echo-planar imaging DWI pulse sequence. Eleven b-values ranging from 0 to 800 s/mm2 were used. The acquisition was separated into blocks (b0, b25), (b0, b50),...(b0, b800) and each block was acquired in a single expirational breath-hold (TA = 26 seconds) to avoid motion artifacts. The ADC was calculated for all b-values using linear regression yielding ADC(tot). By applying the IVIM model, which allows for the estimation of perfusion effects in DWI, the perfusion fraction f and the perfusion free diffusion parameter D were calculated. The diagnostic performance of ADC, f and D as a measure for the differentiation between healthy pancreas and pancreatic carcinoma was evaluated with receiver operating characteristics analysis.

RESULTS

In the healthy control group, the ADC(tot) ranged from 1.53 to 2.01 microm2/ms with a mean value of 1.71 +/- 0.19 microm2/ms, the perfusion fraction f ranged from 18.5% to 40.4% with a mean value of 25.0 +/- 6.2%, and the diffusion coefficient D from 0.94 to 1.28 microm2/ms with a mean value of 1.13 +/- 0.15 microm2/ms. In patients with pancreas carcinoma, the ADC(tot) ranged from 0.98 to 1.81 microm2/ms with a mean value of 1.31 +/- 0.24 microm2/ms, the perfusion fraction f ranged from 0% to 20.4% with a mean value of 8.59 +/- 4.6% and the diffusion coefficient D from 0.74 to 1.60 microm2/ms with a mean value of 1.15 +/- 0.22 microm2/ms. In comparison to healthy pancreatic tissue, a significant reduction of the perfusion fraction f and of ADC(tot) was found in pancreatic carcinoma (P < 0.00001, 0.0002, respectively). The f value showed more than a 10-fold higher significance level in distinguishing cancerous from normal tissue when compared with the ADC(tot) value. No significant difference in the diffusion coefficient D was observed between the 2 groups (P > 0.5). In the receiver operating characteristic-analyses, the area under curve for f was 0.991 and significantly larger than ADC(tot) (P < 0.05). f had the highest sensitivity, specificity, negative predictive value, and positive predictive value with 95.7%, 100%, 93.3%, and 100%, respectively.

CONCLUSIONS

Using the IVIM-approach, the f value proved to be the best parameter for the differentiation between healthy pancreas and pancreatic cancer. The acquisition of several b-values strongly improved the stability of the parameter estimation thus increasing the sensitivity and specificity to 95.7% and 100% respectively. The proposed method may hold great promise for the non invasive, noncontrast-enhanced imaging of pancreas lesions and may eventually become a screening tool for pancreatic cancer.

Decreased blood flow with increased metabolic activity: a novel sign of pancreatic tumor aggressiveness

PURPOSE

To study blood flow (BF) and metabolism in normal pancreas and in different pancreatic lesions. We then determined the effect of these biomarkers on outcome in patients with pancreatic cancer.

EXPERIMENTAL DESIGN

Oxygen-15-labeled water and fluorodeoxyglucose positron emission tomography/computed tomography scans were used in 26 patients with a suspicion of pancreatic cancer to measure pancreatic BF and metabolism. In addition, the ratio of standardized uptake value to BF (SUV/BF) was calculated. Patients were divided into three groups: patients with a finding of normal pancreas (n = 7), benign lesions (n = 8), and malignant tumors (n = 11).

RESULTS

Patients with benign and malignant pancreatic tumors had decreased BF of the lesion by 48% and 60%, respectively, compared with patients with normal pancreatic tissue. SUV(max) was 3-fold higher in malignant tumors compared with both benign lesions and normal pancreas (P < 0.05). In contrast, the SUV(max) of patients with benign lesions and normal pancreas did not differ. The SUV/BF ratio was significantly higher in malignant lesions than in benign lesions or in patients with normal pancreas (P < 0.05). In patients with cancer, high SUV/BF ratio was a stronger predictor of poor survival compared with high metabolism or lower-than-normal pancreatic BF.

CONCLUSIONS

BF in pancreatic cancer is significantly reduced compared with the normal pancreas, which may in part explain the poor success of both radiotherapy and chemotherapy. We suggest that the composite measurement of BF and metabolism in pancreatic cancer could serve as a novel tool in the planning of treatments targeting vasculature.

Measurement of canine pancreatic perfusion using dynamic computed tomography: influence of input-output vessels on deconvolution and maximum slope methods

OBJECTIVE

We investigated whether the prerequisite of the maximum slope and deconvolution methods are satisfied in pancreatic perfusion CT and whether the measured parameters between these algorithms are correlated.

METHODS

We examined nine beagles injected with iohexol (200 mgI kg(-1)) at 5.0 ml s(-1). The abdominal aorta and splenic and celiac arteries were selected as the input arteries and the splenic vein, the output veins. For the maximum slope method, we determined the arterial contrast volume of each artery by measuring the area under the curve (AUC) and compared the peak enhancement time in the pancreas with the contrast appearance time in the splenic vein. For the deconvolution method, the artery-to-vein collection rate of contrast medium was calculated. We calculated the pancreatic tissue blood flow (TBF), tissue blood volume (TBV), and mean transit time (MTT) using both algorithms and investigated their correlation based on vessel selection.

RESULTS

The artery AUC significantly decreased as it neared the pancreas (P<0.01). In all cases, the peak time of the pancreas (11.5±1.6) was shorter than the appearance time (14.1±1.6) in the splenic vein. The splenic artery-vein combination exhibited the highest collection rate (91.1%) and was the only combination that was significantly correlated between TBF, TBV, and MTT in both algorithms.

CONCLUSION

Selection of a vessel nearest to the pancreas is considered as a more appropriate prerequisite. Therefore, vessel selection is important in comparison of the semi-quantitative parameters obtained by different algorithms.

Prediction of anastomotic leakage after pancreatic head resections by dynamic magnetic resonance imaging (dMRI)

PURPOSE

The texture of the pancreatic tissue is a main risk factor for leakage after pancreaticojejunostomy and can be differentiated using dynamic contrast enhanced magnetic resonance imaging (dMRI). In order to identify risk factors and to assess the role of pancreatic dMRI, a cohort of patients was retrospectively reviewed.

PATIENTS AND METHODS

One hundred seven consecutive patients were identified in the departmental database and examined by means of a standardized dMRI protocol using a 1.5-T MRI system. Signal intensity (SI) measurements (aorta, body of the pancreas, muscle tissue) were performed in the axial T1-weighted sequences before and after 25 and 60 s after i.v. application of gadolinium-diethylenetriaminepentaacetic acid. For all patients with a standardized contrast medium curve in the aorta (n = 72), a muscle-normalized signal intensity curve (SIC) with SI(ratio) was calculated. SI(ratio)s were classified in two groups: rapid increase (SI(ratio) >or= 1.1, early arterial value > portal-venous value, "soft" pancreas) and delayed increase (SI(ratio) <1.1, "firm" or "hard" pancreas). All patients received pancreatic head resection with a duct-to-mucosa pancreaticojejunostomy. The dMRI data was correlated with prospectively acquired clinical data.

RESULTS

Leakage of the pancreaticojejunostomy occurred more frequently (12/37 vs. two of 35, 32% vs. 6%, p = 0.006) in patients with a rapid increase and an SI(ratio) >or= 1.1 ("soft" pancreas, n = 37) compared to those with delayed perfusion (SI(ratio) <1.1, "hard" pancreas, n = 35). The more severe type B and C anastomotic leakages occurred only in the group of patients with SI(ratio) >or= 1.1. Patients with a rapid increase had significantly better preoperative American Society of Anesthesiologists staging, lower carbohydrate antigen 19-9 values, and smaller tumor sizes. Most of them had not only benign tumors but also longer postoperative hospital stay, in comparison to patients with delayed perfusion (SI(ratio) <1.1). Multivariate analysis revealed SI(ratio) of >or=1.1 to be the only preoperative parameter predicting leakage significantly with an odds ratio of 7.9.

CONCLUSION

dMRI with SI(ratio) calculation provided reliable information for the prediction of pancreatic texture. Patients with a SI(ratio) >or= 1.1 had a 7.9-fold increased risk of anastomotic leakage and a prolonged hospital stay. SIC with measurements of SI(ratio) in dMRI could therefore define patients at risk for anastomotic leakage.

Perfusion imaging of the pancreas using an arterial spin labeling technique

PURPOSE

To investigate the feasibility of perfusion imaging of the pancreas using an arterial spin labeling (ASL) technique.

MATERIALS AND METHODS

An adapted flow-sensitive alternating inversion recovery (FAIR)-TrueFISP ASL technique was implemented on a 1.5 T scanner. Anatomical and perfusion imaging in three different parts of the pancreas were performed in 10 healthy volunteers. Quantitative perfusion values were calculated using the extended Bloch equations.

RESULTS

Perfusion images of all subjects showed diagnostic image quality in the pancreatic tail and the head. Assessment of pancreatic tissue perfusion was possible in all organ parts. Mean perfusion values were 271 +/- 79 mL/100g/min in the head, 351 +/- 112 mL/100g/min in the body, and 243 +/- 55 mL/100g/min in the tail of the pancreas. Total examination time for perfusion imaging of the entire organ was 15.4 minutes.

CONCLUSION

FAIR-TrueFISP permits analysis of pancreatic tissue perfusion with good image quality in a clinically applicable measuring time. Assessment of perfusion disorders may be useful in the diagnosis of inflammatory pancreatic pathologies, endocrine and exocrine pancreatic disorders, and in monitoring of pancreatic transplants.

[Tumor-like lesion of the pancreas in chronic pancreatitis : imaging characteristics of computed tomography]

OBJECTIVE

The aim of this study was to describe the imaging findings for inflammatory pseudotumors in patients with chronic pancreatitis as detected in computed tomography (CT).

MATERIALS AND METHODS

In this retrospective study 20 patients with chronic pancreatitis were included, who underwent an abdominal CT scan. In all patients the diagnosis was confirmed by surgery and histopathology. Imaging findings which have previously been described as typical for chronic pancreatitis and for inflammatory pseudotumors were assessed by two radiologists in consensus. Values of tissue density (HU) at CT were measured within the lesions and in the surrounding pancreatic tissue.

RESULTS

In 90% of patients with histologically proven chronic pancreatitis, CT showed corresponding indicative findings. In 10 patients the resected specimen revealed an inflammatory pseudotumor, which was located in all cases within the pancreatic head. Using CT these 10 patients presented with calcifications within the lesion in 50% of the cases, an irregular dilatation of the main pancreatic duct in 90%, a "double duct sign" in 70%, an interrupted main pancreatic duct in the area of the lesion in 50%, a "duct penetrating sign" in 30%, an infiltration of adjacent structures in 10% and pathologically enlarged lymph nodes in 100% of the cases. In the venous contrasting phase six tumors were hypodense and four isodense compared to the surrounding pancreatic tissue. In six patients biphasic CT was performed and the mean difference in attenuation between inflammatory pseudotumors and surrounding parenchyma was significantly higher in the pancreatic phase than in the venous phase.

DISCUSSION

Differentiation between inflammatory pseudotumors and adenocarcinoma remains difficult or even impossible. Typical signs indicative of an adenocarcinoma of the pancreatic head, such as dilatation of the common bile duct and/or the main pancreatic duct as well as enlarged lymph nodes, were also found in patients with inflammatory pseudotumors. Inflammatory pseudotumors showed low contrast between lesions and parenchyma in the venous phase and calcifications within the solid part of the tumor.