Contrast-enhanced ultrasonographic detection of small pancreatic insulinoma

[Modern sonographic imaging of abdominal neuroendocrine tumors]

BACKGROUND

Radiological and nuclear medical diagnostics play an important role in the work-up of patients with gastroenteropancreatic neuroendocrine tumors (GEP-NET). The sonographic examination, including contrast-enhanced examination, depicts an initial imaging modality to screen for NET. This report describes the sonomorphological behavior of ileal and pancreatic NET as well as hepatic metastases from NET.

CLINICAL/METHODICAL ISSUE

Sonographic evaluation of NET of the small intestine, pancreas and neuroendocrine hepatic metastases.

STANDARD RADIOLOGICAL METHODS

Contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI), unenhanced ultrasonography.

METHODICAL INNOVATIONS

Contrast-enhanced ultrasound (CEUS).

PERFORMANCE

CEUS supports unenhanced ultrasound in the detection of NET and the differential diagnosis of unclear lesions, and is more sensitive for liver metastases (sensitivity according to the literature, 99% vs. 68%) PRACTICAL RECOMMENDATIONS: CEUS allows initial evaluation of NET and differentiation of benign vs. malignant lesions. Nevertheless, CEUS cannot replace more elaborate imaging modalities like CT or MRI for thorough staging examinations.

Ultrasound diagnosis of pancreatic solid tumors

INTRODUCTION

Advances and widespread use of various diagnostic imaging modalities have dramatically improved our ability to visualize and diagnose pancreatic diseases. In particular, ultrasonography in pancreatic diseases plays an important role from screening to diagnosis as a simple and safe examination method.

METHODS

The basic scanning method of transabdominal pancreatic ultrasonography, characterization, and differential diagnosis by ultrasonography including contrast-enhanced ultrasonography (CEUS) for solid pancreatic tumors are reviewed with reference to various papers.

RESULTS

In recent years, the ability to visualize and diagnose pancreatic mass lesions has been dramatically improved with advances in ultrasound equipment. In particular, CEUS using an ultrasound contrast agent has made it possible to evaluate hemodynamics in organs or lesions as well as in the flow signal of arterial blood vessels, and it has played an important role not only in diagnosis of the presence of a lesion but also in the qualitative diagnosis. The enhancement behavior and pattern with CEUS of pancreatic solid tumors is shown in text and Fig. 9. Moreover, the flow chart for diagnosing pancreatic solid tumors with CEUS classifying the enhancement behavior and pattern for pancreatic solid tumors on CEUS is shown (Fig. 10). In meta-analyses, the pooled sensitivity in the differential diagnosis of pancreatic adenocarcinomas and other pancreatic focal masses with CEUS was 86-90%, and the pooled specificity was 75-88%.

CONCLUSION

CEUS is a minimally invasive and useful diagnostic method that can be used to make a simple and quick qualitative diagnosis of pancreatic diseases. CEUS provides a lot of information important for diagnosis, and has led to changes in the conventional diagnostic systems in pancreatic diseases.

Imaging presentation of pancreatic neuroendocrine neoplasms

Abstract

Pancreatic neuroendocrine neoplasms (P-NENs) are the second most common solid pancreatic neoplasms. P-NENs have a wide range of imaging features presentations and they can be detected with typical and atypical imaging presentations. Typical and atypical appearances can be explained by pathologic correlations. P-NENs are generally hypervascular lesions, showing a typical enhancement behavior after contrast media injection during imaging methods, but they could also have different imaging features, creating some difficulty in differential diagnosis. For this reason, radiologists should be aware of different imaging presentations of these neoplasms. Radiological evaluation has a critical role in P-NENs identification, characterization, and staging of these neoplasms, especially in those cases in which surgery is the treatment of choice. The present paper shows, indicating the underlying pathologic correlations, typical and atypical presentations of NENs.

Key Points

• P-NENs have a wide range of imaging features presentations, typical and atypical.

• Pathology could help in better understanding the typical P-NENs appearance at imaging.

• P-NENs are generally hypervascular lesions.

• Radiological evaluation has a critical role in P-NENs identification and management.

• Radiologists should know every type of different imaging presentation of P-NENs to better diagnose these kinds of lesions.

Cross sectional and nuclear medicine imaging of pancreatic insulinomas

Insulinomas are rare neuroendocrine tumors which occur predominantly in the pancreas. Although majority of the insulinomas are benign, over-secretion of insulin by the tumor leads to debilitating hypoglycemic symptoms. The diagnosis is based on clinical and biochemical findings. After the diagnosis is made, the principal challenge lies in locating the tumor because most tumors are solitary and small in size. Locating the tumor is of paramount importance as complete surgical excision is the only curative treatment, and incomplete resection leads to persistence of symptoms. Different preoperative and intraoperative imaging techniques have been used with varying success rates for the insulinoma imaging. Besides localizing the tumor, imaging also helps to guide biopsy, detect metastatic lesions, and perform image-guided therapeutic procedures. This review will discuss the role of different Cross sectional and nuclear medicine imaging modalities in insulinomas.

Description of the use of contrast-enhanced ultrasonography in four dogs with pancreatic tumours

Canine pancreatic tumours are rare compared to human medicine and the detection and differentiation of pancreatic neoplasia is challenging with B-mode ultrasonography, which often leads to late clinical diagnosis and poor prognosis. This case report describes the findings of contrast-enhanced ultrasonography in four dogs with pancreatic adenocarcinoma or insulinoma. B-mode ultrasonography of the pancreas revealed a hypoechoic nodule in three dogs and heterogenous tissue in one dog. Contrast-enhanced ultrasonography was able to differentiate between two tumour types: adenocarcinomas showed hypoechoic and hypovascular lesions, whereas insulinomas showed uniformly hypervascular lesions. Contrast-enhanced ultrasonography findings were confirmed by cytology and/or histopathology. The results demonstrated that contrast-enhanced ultrasonography was able to establish different enhancement patterns between exocrine (adenocarcinoma) and endocrine (insulinoma) tumours in dogs.

Pancreatic neuroendocrine neoplasms: diagnosis and management

Pancreatic neuroendocrine neoplasms are uncommon but rising in incidence. There have been recent changes in the WHO nomenclature and a newly proposed American Joint Committee on Cancer TNM staging, which complement each other. These neoplasms are of great medical and radiological interest because of their diverse presenting features and imaging appearances. There is an increased role for both anatomic and functional imaging in the assessment of these neoplasms. A review of the nomenclature, staging, and imaging is presented in this paper.

Qualitative and quantitative contrast enhanced ultrasonography of the pancreas using bolus injection and continuous infusion methods in normal dogs

Quantitative contrast enhanced ultrasound is a major breakthrough for ultrasound imaging in recent years. However, contrast enhancement of the pancreas is brief with bolus injection. To assess if continuous infusion of Sonazoid^® can prolong the duration of pancreatic enhancement over bolus injections, eight adult dogs received bolus injection and continuous infusion of Sonazoid^® on separate days. Contrast enhanced ultrasound of the pancreatic parenchyma and proximal descending duodenum was performed, and time intensity curves reflecting tissue perfusions were generated. Perfusion parameters- time to initial upslope, peak time, time to wash-out and peak intensity were calculated and evaluated. Fast wash-in to intense peak, followed by rapid wash-out was observed for time intensity curves of bolus injection. With continuous infusion, contrast wash-in to peak intensity was gradual, followed by long plateau and slow wash-out. Median contrast enhancement durations of the pancreas and duodenum were significantly prolonged by continuous infusion from 11 sec (range, 10 to 23 sec) and 16 sec (range, 3 to 43 sec) at bolus injection to 205 sec (range, 170 to 264 sec, P<0.01) and 193 sec (range, 169 to 216 sec, P<0.05), respectively. Median peak intensity of the pancreas was 100.9 MPV (range, 80.2 to 124.3 MPV) at bolus injection and 77.6 MPV (range, 58.2 to 99.5 MPV, P<0.05) at continuous infusion. Prolonged continuous imaging is afforded by continuous infusion of contrast agent. Peak intensity of the pancreas was slightly diminished in continuous infusion, but offered adequate imaging subjectively.

Insulinoma in Dogs: A Review

Insulinomas are rare malignant functional pancreatic tumors of the β cells that retain the ability to produce and secrete insulin. Insulinomas are the most common pancreatic neuroendocrine tumor in dogs that can induce a variety of clinical signs that result from hypoglycemia and secondary neuroglycopenic and adrenergic effects. Diagnosis and treatment is considered challenging, and the prognosis can be extremely variable depending on the therapeutic choices. This review aims to summarize and update classic knowledge with current trends in the diagnosis, treatment, and prognosis of insulinomas.

Tailored imaging of islet cell tumors of the pancreas amidst increasing options

Pancreatic islet cell tumors are neuroendocrine tumors, which can produce hormones and can arise as part of multiple endocrine neoplasia type 1 or von-Hippel-Lindau-disease, two genetically well-defined hereditary cancer syndromes. Currently, technical innovation improves conventional and specific molecular imaging techniques. To organize the heterogeneous results described for the imaging of these tumors, we distinguished three indications (1) imaging of a patient with hormone hypersecretion, (2) search for a pancreatic primary in case of proven neuroendocrine cancer of unknown primary, and (3) screening of asymptomatic mutation carriers. We searched for publications on imaging of islet cell tumors between 1995 and January 2010 and defined a Level of Evidence (LOE) for the applicability of each technique. For each technique, data were analyzed in a Forest plot and arranged per imaging indication and tumor subtype. LOEs are weak for all imaging techniques. Analyses indicate a prominent role for endoscopic ultrasound for all three indications.

Multimodal imaging in functional endocrine pancreatic tumors

Endocrine pancreatic tumors, also known as pancreatic islet tumors, are rare entities of neuroendocrine origin that are located within the pancreas or in its close proximity. Approximately 50% of these tumors secrete biologically active substances that lead to the development of specific clinical syndromes. Once diagnosis has been established on the basis of clinical and laboratory findings, localization of the source of pathologic hormone secretion is warranted. Endocrine pancreatic tumor imaging comprises anatomical imaging modalities, such as ultrasound, computed tomography (CT) and MRI, as well as functional radiological studies, including arterial calcium stimulation with hepatic venous sampling, and functional nuclear medicine imaging modalities, such as scintigraphy and PET. The recent combination of high-resolution anatomic studies and functional imaging, such as PET/CT and single-photon emission CT/CT, allows excellent diagnostic evaluation of pancreatic islet cell tumors and has, therefore, especially high value. Given that none of these imaging methods are exclusively superior to the others, visualization of pancreatic islet cell tumors often requires the combination of different imaging modalities.

Assessment of contrast-enhanced ultrasonography in diagnosis and preoperative localization of insulinoma

OBJECTIVE

This study was to evaluate the value of contrast-enhanced ultrasonography (CEUS) in the diagnosis and preoperative localization of insulinoma and explore the enhancement patterns of the tumors.

METHODS

Unenhanced and contrast-enhanced ultrasonographic examinations of 31 patients who underwent resection of insulinomas were retrospectively reviewed. The diagnosis sensitivity and localization specificity of CEUS for insulinomas were determined. Results of unenhanced ultrasonography and CEUS were compared by Chi-square test.

RESULTS

Unenhanced ultrasonography could display 9 of 37 (24.3%) surgically verified insulinomas in 31 patients, while the diagnosis sensitivity and localization specificity of preoperative CEUS was 33 (89.2%) and 32 (86.5%) of the 37 tumors, respectively. In contrast to the unenhanced ultrasonography, the improvement of CEUS in the diagnosis and preoperative localization of insulinomas was significant (p<0.0001). The enhancement pattern of insulinoma on CEUS was fast wash-in and slow wash-out. All the tumors were homogeneous hypervascularity in the earlier arterial phase, while the tumors still displayed hyperenhancing pattern in the late phase.

CONCLUSION

Our study demonstrates the great potential of CEUS in the diagnosis and preoperative localization of insulinomas. Since CEUS is a convenient, inexpensive, effective and non-invasive modality, the study supports the use of CEUS as a primary tool in the evaluation of patients with insulinomas.

Imaging techniques in pancreatic tumors

Conventional ultrasonography represents the first diagnostic imaging modality for the study of pancreatic tumors. Contrast-enhanced ultrasound has significantly improved the accuracy of first-line examination and may influence the choice of second-line investigations: multidetector computed tomography is considered the gold standard for studying pancreatic solid lesions and tumor staging, while MRI with magnetic resonance cholangiopancreatography allows better study of pancreatic cystic lesions and the ductal system. To definitely diagnose a pancreatic lesion, image-guided fine-needle-aspiration or biopsy are very often required. PET with 18-fluorodeoxyglucose, endoscopic ultrasound and intraoperative ultrasonography remain techniques often employed in the third line. This article reviews the imaging techniques generally used for diagnosing the main pancreatic tumors, and a work-up algorithm is finally proposed.

Contrast-enhanced ultrasound of the pancreas

The introduction of contrast-enhanced ultrasonography (CEUS) has led to major improvements in the diagnostic capabilities of ultrasound (US). The innovative use of CEUS for study of the pancreas has created the need for a definition of the most frequent dynamic features of solid and cystic masses. CEUS is less expensive compared to computed tomography and magnetic resonance imaging and is able to significantly improve the accuracy of US, allowing better characterization and staging of pancreatic pathologies.

Contrast-enhanced sonography of nonfunctioning pancreatic neuroendocrine tumors

OBJECTIVE

Diagnosis of malignancy and prognostic assessment continue to be problems in the management of nonfunctioning pancreatic endocrine tumors. Histologic examination is the reference standard. The aim of our study was to compare B-mode and contrast-enhanced sonographic findings regarding nonfunctioning pancreatic endocrine tumors. Signs of malignancy, such as Ki67 index and presence of hepatic metastasis, were considered.

MATERIALS AND METHODS

We retrospectively reviewed the cases of 38 consecutively registered patients with nonfunctioning pancreatic endocrine tumors evaluated with B-mode and contrast-enhanced sonography and resected. At contrast-enhanced sonography all lesions were divided into hypovascular lesions and isovascular or hypervascular lesions. On the basis of homogeneity of enhancement, lesions were classified as homogeneous and inhomogeneous. During the late phase of contrast enhancement, all solid focal hypoechoic liver lesions detected at contrast-enhanced sonography were considered hepatic metastatic lesions. Among pathologic data, grading, mitotic index, and Ki67 index were evaluated. Spearman's test was used to compare contrast-enhanced sonographic enhancement pattern with pathologic grade.

RESULTS

In the arterial phase, 24 of 38 nonfunctioning pancreatic endocrine tumors (63.1%) were hypervascular, seven (18.4%) were isovascular, and seven (18.4%) were hypovascular. Positive correlation was found between contrast-enhanced sonographic findings and Ki67 index (r(s) = 0.62; p < 0.0001). The difference between contrast-enhanced and B-mode sonography in the diagnosis of nonfunctioning pancreatic endocrine tumors was statistically significant (p < 0.05). Use of contrast-enhanced sonography increased diagnostic confidence in the detection of hepatic metastasis. The areas under the receiver operating characteristic curves were 0.916 for B-mode sonography and 1.000 for contrast-enhanced sonography (p < 0.05). There was moderate positive correlation between contrast-enhanced sonographic enhancement pattern and the presence of hepatic metastasis at diagnosis (r(s) = 0.46; p = 0.004) and between Ki67 index and the presence of hepatic metastasis (r(s) = 0.48; p = 0.0022).

CONCLUSION

The contrast-enhanced sonographic enhancement pattern of nonfunctioning pancreatic endocrine tumors has a positive correlation with Ki67 index, which is considered the most reliable independent predictor of the presence of malignancy.

Advances in radiological imaging of gastrointestinal tumors

This article summarizes the recent advances in radiological imaging in the hepatogastrointestinal field in terms of detection, characterization and staging of tumors. Introduction of multidetector row computed tomography technology has helped computed tomography to excel in its already established indications, and has expanded its capabilities by adding new clinical applications, such as computed tomography angiography, liver perfusion, computed tomography enterography or enteroclysis, and virtual colonoscopy. Contrast-enhanced ultrasound has dramatically changed the role of ultrasound in liver tumor characterization, detection, and other applications. Combining the advantages of unsurpassed soft tissue contrast and lack of ionizing radiation, magnetic resonance imaging of the gastrointestinal tract has become increasingly used clinically. Moreover, substantial progress in molecular and cellular magnetic resonance imaging has been achieved in the past few years. Particularly, the increasing number of available specific contrast agents dedicated to the evaluation of the liver and lymph nodes shows promises in the area of oncologic abdominal imaging.

Ultrasonography of the pancreas. 4. Contrast-enhanced imaging

The introduction of contrast-enhanced ultrasonography (CEUS) has lead to great developments in the diagnostic capabilities of ultrasound. Second generation contrast media, characterized by harmonic responses at low mechanical index of the ultrasound beam, have already proven usefulness in the study of the liver but other abdominal organs can take advantage from the dynamic study during continuous ultrasonographic scans. The dynamic observation of the enhancement allows the perfect evaluation of the abdominal organs perfusion. The perfusion of the pancreas is well correlated to the semeiology of the gland parenchymography at CEUS. The study of the pancreas is a new and promising application of CEUS. CEUS can be used to better identify pancreatic lesions respect to conventional Ultrasound (US) or to characterize pancreatic lesions already visible at US. Moreover the staging of some pancreatic lesions can be improved by the use of contrast media. This article will review the clinical application of CEUS in the different pancreatic pathologies.

Differential diagnosis of non-functional islet cell tumor and pancreatic carcinoma with sonography

OBJECTIVE

To investigate the differential diagnosis of non-functional islet cell tumor (NFICT) and pancreatic ductal adenocarcinoma (pancreatic carcinoma) with clinical presentation and sonographic features.

MATERIALS AND METHODS

Twenty cases of NFICT were investigated in the study, and 41 cases of pancreatic carcinoma were included as the control group. Among them, 5 NFICT and 32 pancreatic carcinomas underwent CEUS with SonoVue. Clinical presentation and sonographic characteristics were evaluated with Logistic regression analysis. Furthermore, the preliminary result of contrast enhanced ultrasound (CEUS) was analyzed.

RESULTS

Statistic analysis showed four significant factors in differential diagnosis for NFICT and pancreatic carcinoma, including age (P<0.001), tumor size (P=0.006), tumor margin (P<0.001) and vascularity of tumor (P=0.004). Combined these four factors, the sensitivity, specificity and accuracy are 95.0%, 95.1% and 95.1%, respectively. When the patient is younger than 60 years, and tumor is smaller than 5 cm with well-defined margin and hypervascular, it would be most likely a NFICT other than pancreatic carcinoma. NFICT often shows early enhancement and more homogeneous infusion than pancreatic carcinoma on CEUS (P=0.005 and 0.008).

CONCLUSIONS

Sonography is able to provide useful differential information for NFICT, which is often misdiagnosed as pancreatic carcinoma.

Microbubble ultrasound contrast agents: an update

Microbubble contrast agents for ultrasound (US) have gained increasing interest in recent years, and contrast-enhanced US (CEUS) is a rapidly evolving field with applications now extending far beyond the initial improvements achieved in Doppler US. This has been achieved as a result of the safe profile and the increased stability of microbubbles persisting in the bloodstream for several minutes, and also by the availability of specialized contrast-specific US techniques, which allow a definite improvement in the contrast resolution and suppression of signal from stationary tissues. CEUS with low transmit power allows real-time scanning with the possibility of prolonged organ insonation. Several reports have described the effectiveness of microbubble contrast agents in many clinical applications and particularly in the liver, spleen, and kidneys. CEUS allows the assessment of the macrovasculature and microvasculature in different parenchymas, the identification and characterization of hepatic and splenic lesions, the depiction of septal enhancement in cystic renal masses, and the quantification of organ perfusion by the quantitative analysis of the echo-signal intensity. Other fields of application include the assessment of abdominal organs after traumas and the assessment of vesico-ureteral reflux in children. Finally, tumor-targeted microbubbles make possible the depiction of specific biologic processes.

Ultrasonography of the pancreas. 7. Intraoperative imaging

The usefulness of intraoperative ultrasonography (IOUS) has been documented in the Literature since the Eighties and, although its main applications are in hepatobiliary and pancreatic surgery, it has been used also in neurosurgery, cardiovascular and endocrine surgery. The continuous technical developments have led to an increase in the diagnostic accuracy of IOUS from the Eighties to now. The use of IOUS has increased in time together with the technical innovations until, mainly in the midnineties, its value was recognized by many surgeons. This results have been obtained with scanners that allow to depict fine anatomical details and detect small lesions in real time with extremely high spatial resolution. IOUS is able to shows fine details, such as primary or secondary lesions not detectable with other preoperative imaging modalities or tumor extension and its relationship with vessels. Assessment of resectability by IOUS may determine important changes in therapeutic planning. The role of IOUS, however, has recently been down-sized, especially in those centers where preoperative imaging is advanced. This article will review the clinical role of pancreatic IOUS in the different pancreatic pathologies.

Multimodality preoperative imaging of pancreatic insulinomas

Pancreatic insulinomas are rare tumours of the islet cells of the pancreas, which account for the majority of functional neuroendocrine tumours of the pancreas. There is often a typical history of recurrent hypoglycaemic collapse and dizzy spells. Insulinomas are usually solitary, and the vast majority are intra-pancreatic in location. They are characteristically small with approximately 66% being less than 2cm at presentation. Insulinomas continue to pose a diagnostic challenge to physicians, surgeons and radiologists alike. The role of imaging is to detect and provide precise anatomical localization and staging of tumours prior to surgery. Due to their small size at clinical presentation, they are notoriously difficult to localize radiologically, and specifically designed protocols are necessary to aid detection. In this review, we describe the current "state of the art" imaging protocols that may be used in the preoperative localization of insulinomas.

Contrast-enhanced ultrasonography of small solid pseudopapillary tumors of the pancreas: enhancement pattern and pathologic correlation of 2 cases

OBJECTIVE

The purpose of this series is to describe the value of contrast-enhanced ultrasonography (CEUS) in the characterization of small pseudopapillary tumors (SPTs) of the pancreas.

METHODS

Two cases of SPTs found on conventional ultrasonography, both located at the pancreatic body, were studied with spiral computed tomography, magnetic resonance imaging, and CEUS. A final diagnosis was obtained with histologic analysis after distal pancreatectomy. Immunohistochemical analysis of the tumors with the CD34 antigen was performed.

RESULTS

At CEUS, the 2 SPTs had a slight peripheral rim enhancement in the early dynamic phases. The presence of this enhancement pattern at CEUS, not clear at spiral computed tomography or at magnetic resonance imaging, suggested the diagnosis of SPTs with a peripheral pseudocapsule deriving from the compression of the pancreatic parenchyma. The presence of a perilesional pseudocapsule was proved at immunohistochemical analysis of the tumors with the CD34 antigen.

CONCLUSIONS

Contrast-enhanced ultrasonography can improve the characterization of SPTs by showing the typical rim enhancement of these pancreatic tumors.

Contrast-enhanced ultrasonography better identifies pancreatic tumor vascularization than helical CT

BACKGROUND

Contrast-enhanced ultrasonography (CEUS) is a recently introduced field of ultrasonography (US). To assess the ability of CEUS to identify the vascularization of solid pancreatic tumors in comparison to helical CT.

METHODS

Forty-two resected pancreatic tumors, found at US, were studied with CEUS and helical CT. The tumor enhancement at CEUS was scored in comparison to the baseline aspect of the lesion and/or the extralesional pancreatic parenchyma together with the adjacent vessels during the dynamic study. All the lesions underwent pathological examination using H&E stains and CD34 markers with an evaluation of the microvessel density (MVD). The correlation of CEUS and helical CT with the MVD of the lesions was established with Spearman's test.

RESULTS

The correlation of CEUS with the MVD of the lesions was significantly superior (Rs = 0.914; p < 0.0001) to that of helical CT (Rs = 0.635; p < 0.0001).

CONCLUSIONS

CEUS is better than helical CT in the identification of the vascularization of solid pancreatic tumors. CEUS, when the pancreatic gland is optimally visualized, should be therefore considered a complementary imaging modality in the characterization of pancreatic tumors. CEUS can be a valid onco-imaging modality for quantifying tumoral vascularization in a noninvasive and accurate way.