Elsevier

Clinical Radiology

Volume 62, Issue 12, December 2007, Pages 1142-1153
Clinical Radiology

review
A clinical algorithm for the assessment of pancreatic lesions: utilization of 16- and 64-section multidetector CT and endoscopic ultrasound

https://doi.org/10.1016/j.crad.2007.05.006Get rights and content

Pancreatic masses may be solid or cystic, benign or malignant, and their characterization can often be difficult as there is considerable overlap in their imaging features. Multidetector computed tomography (MDCT) with multiplanar reconstructions offers improved resolution and optimum visualization of the peripancreatic vasculature, which has improved the accuracy in predicting surgical resectability. Endoscopic ultrasound (EUS) is valuable in the detection of tumours not identified on CT. It is also accurate in identifying vascular involvement, which complements MDCT in predicting resectability. In cases of diagnostic uncertainty, EUS-guided fine-needle aspiration (FNA) can be used to obtain tissue samples from solid lesions and fluid aspirates from cystic lesions, allowing histological, cytological, and biochemical analysis to determine the nature of the lesion. This article focuses on the MDCT and EUS appearances of common pancreatic malignancies, highlighting their relative advantages and their complementary role in detecting and characterizing pancreatic masses. A clinical algorithm for the assessment of pancreatic malignancy, as practised in our institution, is outlined.

Introduction

The role of preoperative imaging in pancreatic malignancy is to identify a pancreatic lesion, determine its malignant potential, and assess its resectability. Pancreatic masses may be solid or cystic, benign or malignant. Solid masses are usually malignant and include ductal adenocarcinoma, accounting for 90% of pancreatic malignancy,1 and neuroendocrine tumours. However, chronic focal pancreatitis can give similar appearances.2, 3 The commonest pancreatic cystic mass by far is a pseudocyst. Cystic tumours comprise 10–15% of all cystic masses and 1–5% of all pancreatic malignancies.4 Overlap exists in the imaging features of benign and malignant cystic lesions, and additionally solid pancreatic tumours with cystic degeneration can mimic primary cystic tumours (Fig. 1). Thus differentiation of benign from malignant solid or cystic pancreatic masses is often difficult.

Contrast-enhanced, single-section, helical CT is almost 100% accurate in determining unresectability, but is less accurate in predicting resectability.1, 5, 6, 7, 8 However, the latest multidetector computed tomography (MDCT) technology provides three-dimensional multiplanar reconstruction techniques enabling accurate determination of tumour involvement of the common bile duct (CBD), pancreatic duct, and peripancreatic vasculature.9, 10, 11, 12 This has improved the preoperative determination of surgical resectability, particularly in relation to vascular invasion.

Although CT is better for the evaluation of distant metastases and the staging of larger tumours, endoscopic ultrasound (EUS) has been shown to be more accurate for local staging and for predicting vascular invasion and tumour resectability, particularly in tumours less than 3 cm.13, 14, 15 Furthermore, EUS enables aspiration and/or biopsy of the pancreatic mass at the same examination allowing a histological diagnosis to be made and differentiation of benign from malignant masses (Fig. 2).

In this article we review the imaging findings of the common pancreatic malignancies and highlight the relative advantages that MDCT and EUS have in relation to one another in the investigation of pancreatic malignancy, in obtaining a diagnosis, and predicting resectability. The role of magnetic resonance cholangiopancreatography (MRCP) and positron emission tomography (PET) in specific situations is also discussed. Finally, a clinical algorithm is provided for the assessment of pancreatic malignancy, as practised in our institution.

Section snippets

Imaging technique

At our centre, CT examinations are performed on 16- and 64-section MDCT (Somatom Sensation, Siemens, Munich, Germany) and reviewed on proprietary workstations using multiplanar reconstructions. Images are obtained following the oral administration of 300 ml water and 100 ml intravenous iopamidol (300 mg/ml) administered by pump injector at a rate of 3–4 ml/s. Images are acquired in the pancreatic and portal venous phases of contrast enhancement (40 and 70 s post-injection, respectively) using 0.75 mm

Cystic lesions

Cystic lesions of the pancreas can essentially be classified according to malignant potential into mucinous and non-mucinous. Mucinous tumours are either overtly malignant or have a definite malignant potential, and therefore, require surgical resection. They have recently been classified into mucinous cystic neoplasms (MCN) and intraductal papillary mucinous neoplasm (IPMN).16 Non-mucinous cysts include neoplastic cysts (serous cystadenoma), inflammatory cysts (pseudocysts) and epithelial

Solid lesions

Solid pancreatic masses include malignancies such as ductal adenocarcinoma, neuroendocrine tumours, lymphoma, and metastases, and benign masses such as focal chronic pancreatitis.

Conclusion

MDCT is excellent for determining non-resectability and for accurately staging pancreatic malignancies. Moreover the improved resolution, particularly in the z-axis for 64-section MDCT, enables high-quality multiplanar reconstructions to be generated. Combined with the fast acquisition time, which allows optimum visualization of both the arterial and venous anatomy, this technique can improve the preoperative prediction of resectability, particularly in relation to vascular involvement.

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