Pancreatic neuroendocrine neoplasms: Magnetic resonance imaging features according to grade and stage

AIMTo describe magnetic resonance (MR) imaging features of pancreatic neuroendocrine neoplasms (PanNENs) according to their grade and tumor-nodes-metastases stage by comparing them to histopathology and to determine the accuracy of MR imaging features in predicting their biological behavior.METHODSThis study was approved by our institutional review board; requirement for informed patient consent was waived due to the retrospective nature of the study. Preoperative MR examinations of 55 PanNEN patients (29 men, 26 women; mean age of 57.6 years, range 21-83 years) performed between June 2013 and December 2015 were reviewed. Qualitative and quantitative features were compared between tumor grades and stages determined by histopathological analysis.RESULTSIll defined margins were more common in G2-3 and stage III-IV PanNENs than in G1 and low-stage tumors (P < 0.001); this feature had high specificity in the identification of G2-3 and stage III-IV tumors (90.3% and 96%, 95%CI: 73.1-97.5 and 77.7-99.8). The mean apparent diffusion coefficient value was significantly lower in G2-3 and stage III-IV lesions compared to well differentiated and low-stage tumors (1.09 × 10-3 mm2/s vs 1.45 × 10-3 mm2/s and 1.10 × 10-3 mm2/s vs 1.53 × 10-3 mm2/s, P = 0.003 and 0.001). Receiving operator characteristic analysis determined optimal cut-offs of 1.21 and 1.28 × 10-3 mm2/s for the identification of G2-3 and stage III-IV tumors, with sensitivity and specificity values of 70.8/80.7% and 64.5/64% (95%CI: 48.7-86.6/60-92.7 and 45.4-80.2/42.6-81.3).CONCLUSIONMR features of PanNENs vary according to their grade of differentiation and their stage at diagnosis and could predict the biological behavior of these tumors.

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 manu-ally drew different regions of interest within the tumor and the adjacent parenchyma to allow the quantita-tive 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 ad-jacent parenchyma. Thus, CEUS allows the quantitative perfusion analysis of pancreatic ductal adenocarcinoma.

Autoimmune pancreatitis:Multimodality non-invasive imaging diagnosis

Autoimmune pancreatitis (AIP) is characterized by obstructive jaundice, a dramatic clinical response to steroids and pathologically by a lymphoplasmacytic infiltrate, with or without a pancreatic mass. Type 1 AIP is the pancreatic manifestation of an IgG4-related systemic disease and is characterized by elevated IgG4 serum levels, infiltration of IgG4-positive plasma cells and extrapancreatic lesions. Type 2 AIP usually has none or very few IgG4-positive plasma cells, no serum IgG4 elevation and appears to be a pancreas-specific disorder without extrapancreatic involvement. AIP is diagnosed in approximately 2%-6% of patients that undergo pancreatic resection for suspected pancreatic cancer. There are three patterns of autoimmune pancreatitis: diffuse disease is the most common type, with a diffuse, &#x0201c;sausage-like&#x0201d; pancreatic enlargement with sharp margins and loss of the lobular contours; focal disease is less common and manifests as a focal mass, often within the pancreatic head, mimicking a pancreatic malignancy. Multifocal involvement can also occur. In this paper we describe the features of AIP at ultrasonography, computed tomography, magnetic resonance and positron emission tomography/computed tomography imaging, focusing on diagnosis and differential diagnosis with pancreatic ductal adenocarcinoma. It is of utmost importance to make an early correct differential diagnosis between these two diseases in order to identify the optimal therapeutic strategy and to avoid unnecessary laparotomy or pancreatic resection in AIP patients. Non-invasive imaging plays also an important role in therapy monitoring, in follow-up and in early identification of disease recurrence.

Prognostication and response assessment in liver and pancreatic tumors:The new imaging

Diffusion-weighted imaging(DWI), dynamic contrastenhanced magnetic resonance imaging(DCE-MRI) and perfusion computed tomography(CT) are technical improvements of morphologic imaging that can evaluate functional properties of hepato-bilio-pancreatic tumors during conventional MRI or CT examinations.Nevertheless, the term "functional imaging" is commonly used to describe molecular imaging techniques, as positron emission tomography(PET)CT/MRI, which still represent the most widely used methods for the evaluation of functional properties of solid neoplasms; unlike PET or single photon emission computed tomography, functional imaging techniques applied to conventional MRI/CT examinations do not require the administration of radiolabeled drugs or specific equipments. Moreover, DWI and DCE-MRI can be performed during the same session, thus providing a comprehensive "one-step" morphological and functional evaluation of hepato-bilio-pancreatic tumors. Literature data reveal that functional imaging techniques could be proposed for the evaluation of these tumors before treatment, given that they may improve staging and predict prognosis or clinical outcome. Microscopic changes within neoplastic tissues induced by treatments can be detected and quantified with functional imaging,therefore these techniques could be used also for posttreatment assessment, even at an early stage. The aim of this editorial is to describe possible applications of new functional imaging techniques apart frommolecular imaging to hepatic and pancreatic tumors through a review of up-to-date literature data, with a particular emphasis on pathological correlations,prognostic stratification and post-treatment monitoring.

Acoustic radiation force impulse of the liver

Acoustic radiation force impulse(ARFI)imaging is a new and promising ultrasound-based diagnostic technique that,evaluating the wave propagation speed,allows the assessment of the tissue stiffness.ARFI is implemented in the ultrasound scanner.By short-duration acoustic radiation forces(less than 1 ms),localized displacements are generated in a selected region of interest not requiring any external compression so reducing the operator dependency.The generated wave scan provides qualitative or quantitative(wave velocity values)responses.Several non-invasive methods for assessing the staging of fibrosis are used,in order to avoid liver biopsy.Liver function tests and transient elastography are non-invasive,sensitive and accurate tools for the assessment of liver fibrosis and for the discrimination between cirrhotic and non-cirrhotic liver.Many published studies analyse ARFI performance and feasibility in studying diffuse liver diseases and compare them to other diagnostic imaging modalities such as conventional ultrasonography and transient elastography.Solid focal liver lesions,both benign and malignant,are common findings during abdominal examinations.The accurate characterization and differential diagnosis are important aims of all the imaging modalities available today.Only few papers describe the application of ARFI technology in the study of solid focal liver lesions,with different results.In the present study,the existing literature,to the best of our knowledge,about ARFI application on diffuse and focal liver pathology has been evaluated and results and statistical analyses have been compared,bringing to the conclusion that ARFI can be used in the study of the liver with similar accuracy as transient elastography in diagnosing significant fibrosis or cirrhosis and has got some advantages in respect to transient elastography since it does not require separate equipment,better displays anatomical structures and measurements can be successfully carried out almost in every patient.

Noninvasive diagnosis of cirrhosis:A review of different imaging modalities

Progressive hepatic fibrosis can lead to cirrhosis,so its early detection is fundamental.Staging fibrosis is also critical for prognosis and management.The gold standard for these aims is liver biopsy,but it has several drawbacks,as it is invasive,expensive,has poor acceptance,is prone to inter observer variability and sampling errors,has poor repeatability,and has a risk of complications and mortality.Therefore,non-invasive imaging tests have been developed.This review mainly focuses on the role of transient elastography,acoustic radiation force impulse imaging,and magnetic resonance-based methods for the noninvasive diagnosis of cirrhosis.

Liver volumetry:Is imaging reliable?Personal experience and review of the literature

The amount of the future liver remnant volume is fun-damental for hepato-biliary surgery, representing animportant potential risk-factor for the development ofpost-hepatectomy liver failure. Despite this, there isno uniform consensus about the amount of hepaticparenchyma that can be safely resected, nor about themodality that should be chosen for this evaluation. Thepre-operative evaluation of hepatic volume, along witha precise identification of vascular and biliar anatomyand variants, are therefore necessary to reduce surgi-cal complications, especially for extensive resections.Some studies have tried to validate imaging methods[ultrasound, computed tomography(CT), magneticresonance imaging] for the assessment of liver volume,but there is no clear evidence about the most accuratemethod for this evaluation. Furthermore, this volumet-ric evaluation seems to have a certain degree of error,tending to overestimate the actual hepatic volume,therefore some conversion factors, which should givea more reliable evaluation of liver volume, have been proposed. It is widespread among non-radiologists the use of independent software for an off-site volumetric analysis, performed on digital imaging and communica-tions in medicine images with their own personal com-puter, but very few studies have provided a validation of these methods. Moreover, while the pre-transplanta-tion volumetric assessment is fundamental, it remains unclear whether it should be routinely performed in all patients undergoing liver resection. In this editorial the role of imaging in the estimation of liver volume is dis-cussed, providing a review of the most recent literature and a brief personal series of correlations between liver volumes and resection specimens' weight, in order to assess the precision of the volumetric CT evaluation.

Percutaneous ablation of pancreatic cancer

Pancreatic ductal adenocarcinoma is a highly aggressive tumor with an overall 5-year survival rate of less than 5%. Prognosis and treatment depend on whether the tumor is resectable or not, which mostly depends on how quickly the diagnosis is made. Chemotherapy and radiotherapy can be both used in cases of nonresectable pancreatic cancer. In cases of pancreatic neoplasm that is locally advanced, non-resectable, but non-metastatic, it is possible to apply percutaneous treatments that are able to induce tumor cytoreduction. The aim of this article will be to describe the multiple currently available treatment techniques(radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation), their results, and their possible complications, with the aid of a literature review.

Diffusion-weighted imaging of pancreatic cancer

Magnetic resonance imaging(MRI) is a reliable and accurate imaging method for the evaluation of patients with pancreatic ductal adenocarcinoma(PDAC). Diffusion-weighted imaging(DWI) is a relatively recent technological improvement that expanded MRI capabilities, having brought functional aspects into conventional morphologic MRI evaluation. DWI can depict the random diffusion of water molecules within tissues(the so-called Brownian motions). Modifications of water diffusion induced by different factors acting on the extracellular and intracellular spaces, as increased cell density, edema, fibrosis, or altered functionality of cell membranes, can be detected using this MR sequence. The intravoxel incoherent motion(IVIM) model is an advanced DWI technique that consent a separate quantitative evaluation of all the microscopic random motions that contribute to DWI, which are essentially represented by molecular diffusion and blood microcirculation(perfusion). Technological improvements have made possible the routine use of DWI during abdominal MRI study. Several authors have reported that the addition of DWI sequence can be of value for the evaluation of patients with PDAC, especially improving the staging; nevertheless, it is still unclear whether and how DWI could be helpful for identification, characterization, prognostic stratification and follow-up during treatment. The aim of this paper is to review up-to-date literature data regarding the applications of DWI and IVIM to PDACs.

Comparison of imaging-based and pathological dimensions in pancreatic neuroendocrine tumors

AIM To establish the ability of magnetic resonance(MR) and computer tomography(CT) to predict pathologic dimensions of pancreatic neuroendocrine tumors(Pan NET) in a caseload of a tertiary referral center.METHODS Patients submitted to surgery for Pan NET at the Surgical Unit of the Pancreas Institute with at least 1 preoperative imaging examination(MR or CT scan) from January 2005 to December 2015 were included and data retrospectively collected. Exclusion criteria were: multifocal lesions, genetic syndromes, microadenomas or mixed tumors, metastatic disease and neoadjuvant therapy. Bland-Altman(BA) and Mountain-Plot(MP) statistics were used to compare size measured by each modality with the pathology size. Passing-Bablok(PB) regression analysis was used to check the agreement between MR and CT.RESULTS Our study population consisted of 292 patients. Seventy-nine(27.1%) were functioning Pan NET. The mean biases were 0.17 ± 7.99 mm, 1 ± 8.51 mm and 0.23 ± 9 mm, 1.2 ± 9.8 mm for MR and CT, considering the overall population and the subgroup of non-functioning-Pan NET, respectively. Limits of agreement(LOA) included the vast majority of observations, indicating a good agreement between imaging and pathology. The MP further confirmed this finding and showed that the two methods are unbiased with respect to each other. Considering ≤ 2 cm non-functioning-Pan NET, no statistical significance was found in the size estimation rate of MR and CT(P = 0.433). PBR analysis did not reveal significant differences between MR, CT and pathology.CONCLUSION MR and CT scan are accurate and interchangeable imaging techniques in predicting pathologic dimensions of Pan NET.