**2. CEUS technique and CEUS aspect of the normal pancreas**

For the CEUS examination of the pancreas, usually a 2.4 ml bolus of SonoVue is injected in an antecubital vein, followed by a 10 ml bolus saline solution. Contrast‐specific US modes are required for the contrast study. They are available on specific ultrasound systems and are generally based on the cancellation and separation of linear US signals from the tissue and use of the nonlinear response from the contrast agent microbubbles [1].

The examination is performed with low mechanical index, using conventional image for orientation, and following in the same time the contrast study in a specific window. A "real‐ time" dynamic observation of the contrast‐enhanced phases – arterial (early stage of enhance‐ ment, until 30 s) and late (delayed stage of enhancement, 30–45 until 120 s following contrast injection) – begins immediately after the contrast bolus [1]. The following aspects are followed up during CEUS: timing and intensity of enhancement and the distribution of the contrast agent.

Approximately 25–40 s following the contrast bolus, the pancreas shows a homogeneous intense enhancement due to its rich vascularity (**Figure 1**) [8]. Also due to the rich vascularity, the pancreas has a rapid "wash‐out," and 2 min following the contrast bolus, the pancreas appears as hypoenhancing as compared to the nearby liver (**Figure 2**) [8]. Thus, CEUS is useful especially for delineation of avascular pancreatic lesions.

On the other hand, US is a useful tool to identify pancreatic lesions, but ultrasound alone is not enough for the differential diagnosis and staging of the identified lesions, especially if a

Contrast‐enhanced ultrasound (CEUS) is not useful for the detection of focal pancreatic lesions, either solid or liquid. It is useful for the characterization of ultrasound‐detected lesions at this level [1]. The technique can be used in acute and chronic pancreatitis (CP), in the characteri‐ zation of solid tumors: ductal adenocarcinoma or neuroendocrine tumors, in the characteri‐

When a pancreatic tumor is detected, an immediate and correct differential diagnosis is mandatory to establish the appropriate management [2]. Conventional ultrasound followed by CEUS can provide a rapid assessment of the pancreatic lesion's pattern and can charac‐ terize the vascularization, thus making possible a differential diagnosis immediately after

CEUS has the advantage of being a real‐time imaging method that allows continuous visual‐ ization of vascular enhancement pattern, as opposed to contrast‐enhanced (CE) computer tomography (CT) or magnetic resonance imaging (MRI), which only take snapshots at preset time moments. Due to lack of side effects and irradiation, CEUS can be repeated immediately

The most frequently used ultrasound contrast agent for pancreas examination is SonoVue (Bracco SpA, Milan, Italy), a second generation, strictly intravascular contrast agent, containing sulfur hexafluoride–filled microbubbles encapsulated in a phospholipid shell. US contrast agents have no influence on micro‐vascularity and can be also used in patients with renal failure, and also allergic reactions are exceptionally rare [2, 3], as opposed to contrast‐enhanced

For the CEUS examination of the pancreas, usually a 2.4 ml bolus of SonoVue is injected in an antecubital vein, followed by a 10 ml bolus saline solution. Contrast‐specific US modes are required for the contrast study. They are available on specific ultrasound systems and are generally based on the cancellation and separation of linear US signals from the tissue and use

The examination is performed with low mechanical index, using conventional image for orientation, and following in the same time the contrast study in a specific window. A "real‐ time" dynamic observation of the contrast‐enhanced phases – arterial (early stage of enhance‐ ment, until 30 s) and late (delayed stage of enhancement, 30–45 until 120 s following contrast injection) – begins immediately after the contrast bolus [1]. The following aspects are followed up during CEUS: timing and intensity of enhancement and the distribution of the contrast

**2. CEUS technique and CEUS aspect of the normal pancreas**

of the nonlinear response from the contrast agent microbubbles [1].

malignant tumor is suspected.

142 Challenges in Pancreatic Pathology

detection.

if inconclusive.

CT/MRI [4–7].

agent.

zation of pseudocysts or pancreatic cystic tumors.

**Figure 1.** CEUS of the normal pancreas, arterial phase: homogeneous intense enhancement (AO—aorta).

**Figure 2.** CEUS of the normal pancreas, late phase: the pancreas is hypoenhancing as compared to the liver (PV—por‐ tal vein; WD—Wirsung duct).
