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 1AIP is the pancreatic manifestation of an Ig G4-related systemic disease and is characterized by elevated Ig G4serum levels,infiltration of Ig G4-positive plasma cells and extrapancreatic lesions.Type 2 AIP usually has none or very few Ig G4-positive plasma cells,no serum Ig G4 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,"sausage-like"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 resonanceand 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.

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.

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.