Updated imaging nomenclature for acute pancreatitis. AJR Am J Roentgenol. 2014;203:W464-W469. [PMID: 25341160 DOI: 10.2214/ajr.13.12222]

Pancreatic Walled-Off Necrosis: Cross-Sectional Imaging Depiction of Debris Predicts the Success of Endoscopic Drainage Using Lumen-Apposing Metal Stents

INTRODUCTION

The use of endoscopic ultrasound (EUS)-guided transmural stent placement for pancreatic walled-off necrosis (WON) drainage is widespread. This study retrospectively analyzed imaging parameters predicting the outcomes of WON endoscopic drainage using lumen-apposing metal stents (LAMS).

METHODS

This study analyzed the data of 115 patients who underwent EUS-guided debridement using LAMS from 2011 to 2015. Pre-intervention CT or MRI was used to analyze the total volume of WON, percentage of debris, multilocularity, and density. Success measures included technical success, the number of endoscopic sessions, the requirement of percutaneous drainage, long-term success, and recurrence.

RESULTS

The primary cause of pancreatitis was gallstones (50.4%), followed by alcohol (27.8%), hypertriglyceridemia (11.3%), idiopathic (8.7%), and autoimmune (1.7%). The mean WON size was 674 mL. All patients underwent endoscopic necrosectomy, averaging 3.1 sessions. Stent placement was successful in 96.5% of cases. Procedural complications were observed in 13 patients (11.3%) and 6 patients (5.2%) who needed additional percutaneous drainage. No patients reported recurrent WON posttreatment. Univariate analysis indicated a significant correlation between debris percentage and the need for additional drainage and long-term success (p < 0.001). The number of endoscopic sessions correlated significantly with debris percentage (p < 0.001).

CONCLUSION

Pre-procedural imaging, particularly debris percentage within WON, significantly predicts the number of endoscopic sessions, the need for further percutaneous drainage, and overall long-term success.

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

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

Feasibility of using software-aided selection of virtual monoenergetic level for optimal image quality of acute necrotising pancreatitis based on dual-energy computed tomography: a preliminary study

OBJECTIVE

This study aimed to assess the feasibility of software-aided selection of monoenergetic level for acute necrotising pancreatitis (ANP) depiction compared to other automatic image series generated using dual-energy computed tomography (CT).

METHODS

The contrast-enhanced dual-source dual-energy CT images in the portal venous phase of 48 patients with ANP were retrospectively analysed. Contrast-to-noise ratio (CNR) of pancreatic parenchyma-to-necrosis, signal-to-noise ratio (SNR) of the pancreas, image noise, and score of subjective diagnosis were measured, calculated, and compared among the CT images of 100 kV, Sn140 kV, weighted-average 120 kV, and optimal single-energy level for CNR.

RESULTS

CNR of pancreatic parenchyma-to-necrosis in the images of 100 kV, Sn140 kV, weighted-average 120 kV, and the optimal single-energy level for CNR was 5.18 ± 2.39, 3.13 ± 1.35, 5.69 ± 2.35, and 9.99 ± 5.86, respectively; SNR of the pancreas in each group was 6.31 ± 2.77, 4.27 ± 1.56, 7.21 ± 2.69, and 11.83 ± 6.30, respectively; image noise in each group was 18.78 ± 5.20, 17.79 ± 4.63, 13.28 ± 3.13, and 9.31 ± 2.96, respectively; and score of subjective diagnosis in each group was 3.56 ± 0.50, 3.00 ± 0.55, 3.48 ± 0.55, and 3.88 ± 0.33, respectively. The four measurements of the optimal single-energy level for CNR images were significantly different from those of images in the other three groups (P < 0.05). CNR of pancreatic parenchyma-to-necrosis, SNR of the pancreas, and score of subjective diagnosis in the images of the optimal single-energy level for CNR were significantly higher, while the image noise was lower than those in the other three groups (all P = 0.000).

CONCLUSION

Optimal single-energy level imaging for CNR of dual-source CT could improve quality of CT images in patients with ANP, enhancing the display of necrosis in the pancreas.

Natural Course of Early Detected Acute Peripancreatic Fluid Collection in Moderately Severe or Severe Acute Pancreatitis

Background and Objectives: Acute peripancreatic fluid collection (APFC) is an acute local complication of acute pancreatitis (AP) according to the revised Atlanta classification. Sometimes APFC resolves completely, sometimes it changes into a pseudocyst or walled-off necrosis (WON), so called late complications. The aim of this study is to investigate the natural course of APFC detected on early computed tomography (CT) in moderately severe (MSAP) or severe AP (SAP). Materials and Methods: From October 2014 to September 2015, patients with MSAP or SAP were enrolled if there was APFC within 48 h of onset on imaging studies at six medical centers. The status of fluid collection was followed 4–8 weeks after onset. Initial laboratory findings, CT findings and clinical scoring systems were analyzed. Results: A total of 68 patients were enrolled and APFC was completely resolved in 32 (66.7%) patients in the MSAP group and 9 (34.6%) in the SAP group. Patients with a high bedside index for severity in acute pancreatitis (BISAP) score (≥3 points) were common in the SAP group. C-reactive protein (CRP) after 48 h from admission and BUN level were also high in the SAP group. In multivariate analysis, BISAP score (≥3 points), elevation of CRP after 48 h (≥150 mg/L) and nasojejunal feeding after 48 h were risk factors for the development of late complications. Conclusions: Spontaneous resolution of APFC was more common in MSAP group and APFC can be changed to pseudocyst or WON in patients with elevated BISAP score, CRP level after 48 h, and non-improved abdominal pain.

Use of MR in Pancreaticobiliary Emergencies

This article presents the MR protocols, imaging features, diagnostic criteria, and complications of commonly encountered emergencies in pancreaticobiliary imaging, which include pancreatic trauma, bile leak, acute cholecystitis, biliary obstruction, and pancreatitis. Various classifications and complications that can arise with these conditions, as well as artifacts that may mimic pathology, are also included. Finally, the emerging utility of abbreviated MR protocols is discussed.

Magnetic Resonance Imaging-Based Radiomics Models to Predict Early Extrapancreatic Necrosis in Acute Pancreatitis

OBJECTIVE

The aim of the study was to investigate radiomics models based on magnetic resonance imaging (MRI) for predicting early extrapancreatic necrosis (EXPN) in acute pancreatitis.

METHODS

Radiomics features were extracted from T2-weighted images of extrapancreatic collections and late arterial-phase images of the pancreatic parenchyma for 135 enrolled patients (94 in the primary cohort, including 47 EXPN patients and 41 in the validation cohort, including 20 EXPN patients). The optimal features after dimension reduction were used for radiomics modeling through a support vector machine. A clinical model, the MR severity index score, and extrapancreatic inflammation on MRI were evaluated.

RESULTS

Twelve optimal features from the extrapancreatic collection images and 10 from the pancreatic parenchyma images were selected for modeling. The pancreatic parenchyma-based and extrapancreatic collection-based radiomics models showed good predictive accuracy in both the training and validation cohorts. The areas under the curve of the extrapancreatic collection-based radiomics model (0.969 and 0.976) were consistent with those of the pancreatic parenchyma-based model (0.931 and 0.921) for both cohorts and better than those of the clinical model and imaging scores for both cohorts.

CONCLUSIONS

The MRI-based radiomics models of both the extrapancreatic collections and the pancreatic parenchyma had excellent predictive performance for early EXPN.

[Acute pancreatitis : Typical findings in computed tomography and magnetic resonance imaging]

CLINICAL PROBLEM

Imaging plays a major role to differentiate interstitial edematous from necrotic pancreatitis and to describe relevant local complications for proper patient management and decision-making in acute pancreatitis.

STANDARD RADIOLOGICAL PROCEDURES

The revised Atlanta classification 2012 of acute pancreatitis divides patients into mild, moderately severe and severe groups. Computed tomography (CT) and magnetic resonance imaging (MRI) are well established for diagnosis and follow-up of acute pancreatitis and its complications METHODOLOGICAL INNOVATIONS AND ASSESSMENT: Based on the revised Atlanta classification, CT and MRI allow for adequate categorization of interstitial edematous and necrotic pancreatitis. Imaging and standardized reporting nomenclature enable confident differentiation of early and late complications in acute pancreatitis.

RECOMMENDATIONS

The aim of this review article is to present an image-rich overview of different morphologic characteristics of acute pancreatitis and associated local complications by CT or MRI using case examples.

Secretin-Enhanced MRCP: How and Why-AJR Expert Panel Narrative Review

Secretin-enhanced MRCP (S-MRCP) has advantages over standard MRCP for imaging of the pancreaticobiliary tree. Through the use of secretin to induce fluid production from the pancreas and leveraging of fluid-sensitive MRCP sequences, S-MRCP facilitates visualization of ductal anatomy, and the findings provide insight into pancreatic function, allowing radiologists to provide additional insight into a range of pancreatic conditions. This narrative review provides detailed information on the practical implementation of S-MRCP, including patient preparation, logistics of secretin administration, and dynamic secretin-enhanced MRCP acquisition. Also discussed are radiologists' interpretation and reporting of S-MRCP examinations, including assessments of dynamic compliance of the main pancreatic duct and of duodenal fluid volume. Established indications for S-MRCP include pancreas divisum, anomalous pancreaticobiliary junction, Santorinicele, Wirsungocele, chronic pancreatitis, main pancreatic duct stenosis, and assessment of complex postoperative anatomy. Equivocal or controversial indications are also described along with an approach to such indications. These indications include acute and recurrent acute pancreatitis, pancreatic exocrine function, sphincter of Oddi dysfunction, and pancreatic neoplasms.

Imaging acute pancreatitis

OBJECTIVES

Acute pancreatitis is common; the clinical course of this potentially severe condition varies widely. This paper aims to review the role of different imaging techniques in the management of acute pancreatitis, describe the main imaging findings for this entity, and explain the terms and criteria used to classify them.

CONCLUSIONS

Imaging techniques play a key role in the management of acute pancreatitis, from diagnosis and staging to identifying and treating complications, as well as in determining the underlying causes of the condition. For these reasons, radiologists should know the advantages and limitations of each imaging technique in the evaluation of acute pancreatitis, be familiar with the wide spectrum of imaging findings associated with it, and how to use the specific terminology derived from the Atlanta classification to ensure the standardization and quality of reports.

Acute pancreatitis: A pictorial review of early pancreatic fluid collections

Acute pancreatitis is a common acute inflammatory disease involving the pancreas and peripancreatic tissues or remote organs. The revised Atlanta classification 2012 of acute pancreatitis divides patients into mild, moderately severe and severe groups. Major changes of the classification include acute fluid collection terminology. However, some inappropriate terms of the radiological diagnosis reports in the daily clinical work or available literature may still be found. The aim of this review article is: to present an image-rich overview of different morphologic characteristics of the early-stage (within 4 wk after symptom onset) local complications associated with acute pancreatitis by computed tomography or magnetic resonance imaging; to clarify confusing imaging concepts for pancreatic fluid collections and underline standardised reporting nomenclature; to assist communication among treating physicians; and to facilitate the implications for clinical management decision-making.

MRI in acute pancreatitis

Computed tomography (CT) is the most commonly performed imaging test for acute pancreatitis. Nevertheless, magnetic resonance (MRI) imaging is useful in many specific situations. These include evaluating patients with acute pancreatitis who cannot receive iodinated CT contrast, elucidating the underlying cause of acute pancreatitis, assessing ductal disconnection and for guiding intervention of necrotic collections. Non-contrast MRI is superior to non-contrast CT and MRI for the diagnosis of acute pancreatitis. We discuss these specific uses of MRI in acute pancreatitis. We highlight the future advances in MRI including faster, free-breathing scans that allow MRI to be completed within 10 min.

Reporting of acute pancreatitis by radiologists-time for a systematic change with structured reporting template

Acute pancreatitis has a wide array of imaging presentations. Various classifications have been used in the past to standardize the terminology and reduce confusing and redundant terms. We aim to review the historical and current classifications of acute pancreatitis and propose a new reporting template which can improve communication between various medical teams by use of appropriate terminology and structured radiology template. The standardized reporting template not only conveys the most important imaging findings in a simplified yet comprehensive way but also allows structured data collection for future research and teaching purposes.

Current concepts for the diagnosis of acute pancreatitis by multiparametric magnetic resonance imaging

Acute pancreatitis is classically characterized by acute chemical inflammation of the pancreatic gland itself, peripancreatic tissues, and even remote organs. The newly revised Atlanta Classification 2012 redefined the patterns of pancreatic necrosis and local complications in acute pancreatitis. The Atlanta Classification's novelty was in emphasizing that extrapancreatic fat necrosis, which leads to walled-off necrosis, is associated with poor prognosis. Conversely, the free fluid liquid was considered to be less related to complications. The Atlanta's classification's main weakness is that it is mainly computed tomography (CT) based, as contrast-enhanced CT is the predominant imaging technique used for evaluating a wide range of pathological processes of acute pancreatitis. However, some local complications are difficult to distinguish accurately on CT. Recent advances, including significantly better soft-tissue contrast, favor multiparametric magnetic resonance imaging (mpMRI) for a more comprehensive assessment of acute pancreatitis pathology, particularly for small necrotic/fat debris within a collection. In addition, the MRI severity index (MRSI), which combines Balthazar's grade points and points of the extent of pancreatic necrosis, has been proven to be crucial for the initial evaluation, staging, and prognosis of acute pancreatitis. Other innovations, such as the recognition of important MRI features in acute pancreatitis and the utilization of newer, more effective terminology for imaging reporting assistance in the differentiation of the common local complications following this disease, have improved the treatment for acute pancreatitis. In this paper, with reference to the 2012 revised Atlanta classification, we review the strengths and limitations of MRI for identifying acute pancreatitis, the MRI findings of a spectrum of pathological entities, and the important local complications secondary to acute pancreatitis.

The hepatoduodenal ligament revisited: cross-sectional imaging spectrum of non-neoplastic conditions

INTRODUCTION

The hepatoduodenal ligament is frequently involved by conditions affecting the portal triad and surrounding structures, including a vast array of non-neoplastic conditions. Due its unique location between the retroperitoneum and the peritoneal space, the hepatoduodenal ligament is also targeted by inflammatory conditions involving the retroperitoneum and the liver. Finally, the presence of lymphatics and of the biliary tracts makes the hepatoduodenal ligament a route of spread for a variety of infections. The purpose of this pictorial essay is twofold: to review the cross-sectional radiological anatomy and variants of the structures within the hepatoduodenal ligament, and to illustrate the non-neoplastic conditions that may arise within the hepatoduodenal ligament.

CONCLUSION

Familiarity with these specific entities and their cross-sectional imaging findings is fundamental for a more accurate diagnosis.

The importance of acoustic radiation force impulse (ARFI) elastography in the diagnosis and clinical course of acute pancreatitis

BACKGROUND/AIMS

Acute pancreatitis (AP) is characterized by acute inflammation of the pancreas and it has a highly variable clinical course. The aim of our study was to evaluate the value of acoustic radiation force impulse (ARFI) elastography in the diagnosis and clinical course of AP.

MATERIALS AND METHODS

Consecutive patients with a diagnosis of AP (patients group) and healthy subject (control group) were prospectively enrolled to the study. Demographic features and clinical, laboratory, and radiological data were recorded. Virtual Touch Tissue Quantification (VTQ) was used to implement ARFI elastography. The tissue elasticity is proportional to the square of the wave velocity (SWV).

RESULTS

A total of 108 patients (age, 57±1.8 y) and 79 healthy subjects (age, 53.6±1.81 y) were included in the study. There were 100 (92.5%) edematous and 8 (7.4%) necrotizing AP. The mean SWV was significantly higher in the patient group than in the control group (2.43±0.08 vs. 1.27±0.025 m/s, p < 0.001). There was not significant difference between patient and control group regarding age and gender. SWV cutoff value of 1.63 m/s was associated with 100% sensitivity and 98% specificity for the diagnosis of AP. There was not significant difference between patients with and without complications and patients with edematous and necrotizing AP regarding mean SWV value. There was also not significant correlation between mean SWV value and age, mean length of hospital stay, and mean amylase level.

CONCLUSION

ARFI elastography may be a feasible method for the diagnosis of AP, but it has no value for the prediction of clinical course of AP.

The clinical value of secretin-enhanced MRCP in the functional and morphological assessment of pancreatic diseases

Secretin-enhanced magnetic resonance cholangiopancreatography (S-MRCP) provides a non-invasive way, with which, to evaluate pancreatic duct (PD) anatomy and exocrine pancreatic function. S-MRCP can be added to the routine pancreas MR examination in equivocal cases. Moreover, it can detect subtle PD involvement, allowing diagnosis of early, rather than end-stage, pancreatic diseases. Although S-MRCP is a valuable non-invasive diagnostic method, it is only performed in a few centres due to relative high cost. Furthermore, less familiarity with its indications, the examination technique, and image interpretation also contribute to its limited use. Thus, the purpose of this article is to explain secretin's mechanism of action, the examination technique, the clinically relevant indications, the advantages, and limitations. Finally, we will focus on image analysis and its role in achieving an early and accurate diagnosis of specific pancreatic and PD diseases.

Pre-clinical Evaluation of a Cyanine-Based SPECT Probe for Multimodal Tumor Necrosis Imaging

PURPOSE

Recently we showed that a number of carboxylated near-infrared fluorescent (NIRF) cyanine dyes possess strong necrosis avid properties in vitro as well as in different mouse models of spontaneous and therapy-induced tumor necrosis, indicating their potential use for cancer diagnostic- and prognostic purposes. In the previous study, the detection of the cyanines was achieved by whole body optical imaging, a technique that, due to the limited penetration of near-infrared light, is not suitable for investigations deeper than 1 cm within the human body. Therefore, in order to facilitate clinical translation, the purpose of the present study was to generate a necrosis avid cyanine-based NIRF probe that could also be used for single photon emission computed tomography (SPECT). For this, the necrosis avid NIRF cyanine HQ4 was radiolabeled with ¹¹¹indium, via the chelate diethylene triamine pentaacetic acid (DTPA).

PROCEDURES

The necrosis avid properties of the radiotracer [¹¹¹In]DTPA-HQ4 were examined in vitro and in vivo in different breast tumor models in mice using SPECT and optical imaging. Moreover, biodistribution studies were performed to examine the pharmacokinetics of the probe in vivo.

RESULTS

Using optical imaging and radioactivity measurements, in vitro, we showed selective accumulation of [¹¹¹In]DTPA-HQ4 in dead cells. Using SPECT and in biodistribution studies, the necrosis avidity of the radiotracer was confirmed in a 4T1 mouse breast cancer model of spontaneous tumor necrosis and in a MCF-7 human breast cancer model of chemotherapy-induced tumor necrosis.

CONCLUSIONS

The radiotracer [¹¹¹In]DTPA-HQ4 possessed strong and selective necrosis avidity in vitro and in various mouse models of tumor necrosis in vivo, indicating its potential to be clinically applied for diagnostic purposes and to monitor anti-cancer treatment efficacy.

Accuracy of contrast-enhanced ultrasound compared with conventional ultrasound in acute pancreatitis: Diagnosis and complication monitoring

Contrast-enhanced ultrasound (CEUS) has been used for diagnosing acute pancreatitis (AP), particularly severe acute pancreatitis (SAP). However, the diagnostic difference between CEUS and conventional ultrasonography (CUS) for AP and SAP has not been reported. The aim of the present study was to investigate the diagnostic accuracy of CUS and CEUS for AP. A total of 196 patients clinically diagnosed with AP were selected. All patients underwent CUS, CEUS and contrast-enhanced computed tomography (CECT) within 72 h. CECT was considered the gold standard. Pancreatic size, peripancreatic fluid collection (PPFC) and splenic vessel complications were the variables observed by CUS and CEUS. The differences in the variables among the three methods were analyzed using the χ² test and statistical analysis software. Significant differences in pancreatic size, PPFC and splenic vessel complications in AP were observed between CEUS and CUS (P<0.05). χ² test results indicated that CEUS significantly differed from CUS in terms of having a higher diagnostic accuracy for AP and SAP (P<0.05). The results indicate that CEUS is a reliable method for the diagnosis and monitoring of AP and SAP, and may be substituted for CECT.

The Necrosis-Avid Small Molecule HQ4-DTPA as a Multimodal Imaging Agent for Monitoring Radiation Therapy-Induced Tumor Cell Death

PURPOSE

Most effective antitumor therapies induce tumor cell death. Non-invasive, rapid and accurate quantitative imaging of cell death is essential for monitoring early response to antitumor therapies. To facilitate this, we previously developed a biocompatible necrosis-avid near-infrared fluorescence (NIRF) imaging probe, HQ4, which was radiolabeled with 111Indium-chloride (111In-Cl3) via the chelate diethylene triamine pentaacetic acid (DTPA), to enable clinical translation. The aim of the present study was to evaluate the application of HQ4-DTPA for monitoring tumor cell death induced by radiation therapy. Apart from its NIRF and radioactive properties, HQ4-DTPA was also tested as a photoacoustic imaging probe to evaluate its performance as a multimodal contrast agent for superficial and deep tissue imaging.

MATERIALS AND METHODS

Radiation-induced tumor cell death was examined in a xenograft mouse model of human breast cancer (MCF-7). Tumors were irradiated with three fractions of 9 Gy each. HQ4-DTPA was injected intravenously after the last irradiation, NIRF and photoacoustic imaging of the tumors were performed at 12, 20, and 40 h after injection. Changes in probe accumulation in the tumors were measured in vivo, and ex vivo histological analysis of excised tumors was performed at experimental endpoints. In addition, biodistribution of radiolabeled [111In]DTPA-HQ4 was assessed using hybrid single-photon emission computed tomography-computed tomography (SPECT-CT) at the same time points.

RESULTS

In vivo NIRF imaging demonstrated a significant difference in probe accumulation between control and irradiated tumors at all time points after injection. A similar trend was observed using in vivo photoacoustic imaging, which was validated by ex vivo tissue fluorescence and photoacoustic imaging. Serial quantitative radioactivity measurements of probe biodistribution further demonstrated increased probe accumulation in irradiated tumors.

CONCLUSION

HQ4-DTPA has high specificity for dead cells in vivo, potentiating its use as a contrast agent for determining the relative level of tumor cell death following radiation therapy using NIRF, photoacoustic imaging and SPECT in vivo. Initial preclinical results are promising and indicate the need for further evaluation in larger cohorts. If successful, such studies may help develop a new multimodal method for non-invasive and dynamic deep tissue imaging of treatment-induced cell death to quantitatively assess therapeutic response in patients.

Imaging lexicon for acute pancreatitis: 2012 Atlanta Classification revisited

The original 1992 Atlanta Classification System for acute pancreatitis was revised in 2012 by the Atlanta Working Group, assisted by various national and international societies, through web-based consensus. This revised classification identifies two phases of acute pancreatitis: early and late. Acute pancreatitis can be either oedematous interstitial pancreatitis or necrotizing pancreatitis. Severity of the disease is categorized into three levels: mild, moderately severe and severe, depending upon organ failure and local/systemic complications. According to the type of pancreatitis, collections are further divided into acute peripancreatic fluid collection, pseudocyst, acute necrotic collection, and walled-off necrosis. Insight into the revised terminology is essential for accurate communication of imaging findings. In this review article, we will summarize the updated nomenclature and illustrate corresponding imaging findings using examples.