at the time this article was written, was a Clinical Fellow and
is an Associate Professor of Radiology at Mallinckrodt Institute
of Radiology, Washington University Medical School, St. Louis,
is an Instructor in the Department of Radiology, International
Medical Center of Japan, Tokyo, Japan.
Magnetic resonance imaging (MRI) is commonly used as a
problem-solving tool for imaging of the pancreas. With recent
advances, such as breath-hold, dynamic contrast-enhanced imaging,
and MR cholangiopancreatography (MRCP), MR is more often used as a
primary imaging modality. MR has an accuracy similar to computed
tomography (CT) in the detection, characterization, and staging of
various pancreatic tumors.
At our institution, the standard MR protocol includes coronal
half-Fourier acquisition single-shot turbo-spin echo (HASTE), axial
in-phase and opposed-phase gradient-recalled echo (GRE), axial T2
turbo-spin echo with fat suppression, or turbo-inversion-recovery
through the liver and pancreas. Two-dimensional (2D) spoiled GRE
with fat suppression and three-dimensional (3D) spoiled GRE with
fat suppression through the pancreas are also obtained. After
administration of gadolinium contrast material at 2 mL/sec, we
obtain breath-hold dynamic 3D spoiled GRE sequence in pancreatic,
portal, and equilibrium phases through the pancreas. We start the
pancreatic phase approximately 25 sec after the start of injection
of contrast material.
The portal phase begins approximately 60 sec, and the equilibrium
phase approximately 100 sec, after the start of injection of the
contrast. If islet cell tumor is suspected, the first phase should
be obtained in the arterial phase, which occurs approximately 10
sec, before the pancreatic phase. We typically perform test bolus
injection to determine the scan delay in this instance. A 2D
spoiled GRE sequence with fat suppression can be used instead of a
3D spoiled GRE sequence for the dynamic study. With the
contrast-enhanced dynamic GRE sequence, we typically cover only the
pancreas to maximize the spatial resolution, and add one delayed
spoiled GRE sequence to cover the entire liver. An MRCP sequence
may be added as necessary before administration of contrast
material. MR cholangiopancreatography is performed using
half-Fourier rapid acquisition with relaxation enhancement (RARE).
A thick-slab technique is used to provide a global view of the
biliary tree and pancreatic duct. Thin-slice technique is useful
for evaluation of detailed anatomy.
Normal MR appearance of the pancreas
On T1-weighted images without fat suppression, the pancreas is
isointense or slightly hyperintense to the liver. With fat
suppression, the normal pancreas is hyperintense to the liver or
other solid organs in the abdomen. High signal intensity on
T1-weighted images is due to the aqueous protein in the glandular
tissue (Figure 1A).
On T2-weighted images, the pancreas has similar signal intensity to
the liver, and is hypointense compared with the spleen or kidneys.
After administration of contrast material, the pancreas enhances
maximally during the pancreatic phase in contrast to the liver,
which shows minimal enhancement during this phase because of its
predominant portal venous supply. During the portal and delayed
phases, the pancreas becomes isointense to the liver (Figures 1B
Congenital and hereditary abnormalities
Pancreas divisum is the most common congenital anomaly of the
pancreas. Divisum occurs as a result of incomplete fusion of the
ventral and dorsal pancreatic ducts. The dorsal pancreatic duct
drains into the duodenum via the minor papilla, separately from the
ventral pancreatic duct and common bile duct. An association
between chronic pancreatitis and pancreas divisum has been
On MRCP, the aberrant drainage of the dorsal pancreatic duct can be
visualized (Figure 2). Annular pancreas is a rare anomaly in which
the pancreas encircles the second portion of the duodenum.
Primary hemochromatosis is characterized by abnormal iron
deposition, which mainly affects the liver, heart, and pancreas.
Involvement of the pancreas occurs in the late stage of the
Because of the magnetic susceptibility effects of iron, the
pancreas becomes hypointense on T2-weighted images and, to a lesser
degree, on T1-weighted images.
Von Hippel-Lindau disease is a phakomatosis that primarily
affects the central nervous system (hemangioblastoma) but may also
affect other organs, including the kidneys, adrenal glands, and
In the pancreas, simple cysts, islet cell tumors, and serous
cystadenomas can be found.
Adenocarcinoma comprises more than 80% of pancreatic neoplasms.
The majority (65%) of pancreatic carcinomas occur in the head of
the pancreas. The prognosis is dismal if the tumor is not resected,
and only 5% to 22% of patients are candidates for curative
resection. Tumors in the head of the pancreas tend to present
earlier than tumors in the body or tail due to obstructive
symptoms. Tumors in the tail and body of the pancreas are rarely
operable. The disease may spread through many pathways, such as:
liver metastasis, lymph node metastasis, peritoneal carcinomatosis,
and direct invasion of the surrounding structures, such as the
celiac artery, superior mesenteric artery, portal vein, bile duct
Absolute contraindications for curative surgery include distant
metastases, peritoneal carcinomatosis, and major arterial
Portal venous involvement is a relative contraindication. In some
cases, a segment of the portal vein may be sacrificed and replaced
with a venous graft.
The main roles of cross-sectional imaging techniques in the
evaluation of patients with suspected pancreatic cancer are lesion
detection, characterization, and staging. MRI has been shown to be
similar or superior to helical CT for these purposes.
Detection and staging of local spread of the disease is best
assessed with dynamic GRE sequences. The tumor appears as an
ill-defined area of hypointensity surrounded by normally enhancing
pancreatic parenchyma in the early phase of enhancement (pancreatic
phase) (Figure 3). Usually, the mass shows a thin rim of faint
enhancement. In the equilibrium phase, the tumor tends to become
isointense to the surrounding normal pancreas. The appearance of
the common bile duct and main pancreatic duct should be evaluated
carefully, particularly when a mass is not visualized in the
pancreas. Dilation of both biliary and pancreatic ducts or abrupt
termination of a dilated duct may suggest the presence of a mass
MR cholangiopancreatography is the best approach for evaluating the
ductal system. For evaluation of vascular invasion, the pancreatic
and venous phases of the dynamic study are useful. Vascular
invasion can be evaluated by the degree of tumor abutment of the
vessels. Data from a CT study suggests that if the tumor abuts more
than half the circumference of the vessel, it is likely that the
vessel is invaded by the tumor (Figure 4). On the other hand, if
the tumor abuts ¾ 25% of the vessel circumference, it is unlikely
that the vessel is invaded by tumor.
When 3D spoiled GRE sequence is used, multiplanar reconstruction
(MPR) or other 3D rendering techniques are useful in assessing
vascular invasion. Liver metastases are slightly hyperintense on
T2-weighted images and hypointense on postcontrast GRE images.
Lymph node metastases are best depicted on T2-weighted images and
postcontrast GRE images. Noncontrast T1-weighted images are also
useful for detecting lymph nodes and assessing vascular encasement
Differentiating between carcinoma and focal pancreatitis can be
extremely difficult. Chronic pancreatitis can cause mass effect and
obstruct either the common bile duct or pancreatic duct. It can
even form an inflammatory mass that is indistinguishable from
carcinoma. In some cases, carcinoma can cause pancreatitis by
obstructing the pancreatic duct, and the pancreatitis can obscure
Islet cell tumors
Islet cell tumors are neuroendocrine in origin, and they can be
functional or nonfunctional. The tumors tend to be smaller when
functional due to earlier presentation. Functional islet cell
tumors include insulinoma, gastrinoma, VIPoma, glucagonoma, and
somatostatinoma. Insulinoma is the most common of the islet cell
tumors. Insulinoma most commonly occurs in the tail of the
pancreas, and its average size at the time of presentation is <2
Gastrinomas tend to be slightly larger than insulinomas and
commonly occur in the head of the pancreas. Islet cell tumors
appear hypointense on T1-weighted fat-suppressed images and
hyperintense on T2-weighted images; they show early arterial
enhancement on dynamic contrast-enhanced images (Figure 5).
Thoeni et al
demonstrated that noncontrast T1-weighted fat-suppressed GRE images
were the most sensitive for lesion detection because of the high
signal intensity of the normal pancreas. Islet cell tumors are
and contrast enhancement may be present at the rim of the cystic
mass. In patients with multiple endocrine neoplasms syndrome, islet
cell tumors are often multiple.
Cystic neoplasms of the pancreas can be divided into two
subgroups: serous cystadenoma and mucinous cystic neoplasms. Serous
cystadenoma is a benign neoplasm, often referred to as microcystic
cystadenoma. It typically consists of clusters of small cysts <2
cm in diameter, although a macrocystic variant has been reported.
On T2-weighted images, serous cystadenoma is a lobulated mass with
very high signal intensity.
The walls of each septa may be imperceptible (Figure 6). Stellate
calcification may be visible as a signal void, although MR is less
sensitive to calcium than CT. After contrast administration,
diffuse faint contrast enhancement can be seen because of wall
enhancement within small cysts. There is considerable overlap in
the imaging appearance of serous and mucinous cystic neoplasm;
therefore, unless the lesion has a completely typical appearance
for serous adenoma, it should be surgically removed.
Mucinous cystic neoplasm is often referred to as macrocystic
cystadenoma or cystadenocarcinoma. Such lesions should be
considered either premalignant or frankly malignant. These lesions
commonly occur in the body or tail of the pancreas in women between
the ages of 40 to 70 years. Mucinous cystic tumors typically
consist of clusters of cysts, with each cyst >2 cm in diameter.
On T2-weighted images, mucinous cystic neoplasms have high signal
intensity and internal septations.
There is no contrast enhancement within the cystic component of the
mass (Figure 7). On T1-weighted images, the cyst may be
hyperintense due to mucin content. The walls of the cystic mass may
be variable in thickness and there may be nodular enhancing areas.
Thick walls and the presence of mural nodules are suggestive of
malignancy, although absence of these findings does not exclude
malignancy. Since it is often very difficult to differentiate
between mucinous adenoma and adenocarcinoma by imaging, mucinous
tumors usually require resection.
Intraductal papillary mucinous tumor (IPMT) is a subtype of the
mucinous cystic neoplasms. The tumor arises from the epithelium of
the main pancreatic duct or its branches, and grows into the
pancreatic duct in a papillomatous pattern. The tumor produces
copious amounts of mucin; thus the tumor is often referred to as
mucin hypersecreting tumor of the pancreas. The hallmark of the
main-duct type IPMT is dilatation of the main pancreatic duct,
which may be indistinguishable from chronic pancreatitis (Figure
8). On MRCP, pancreatic duct dilatation is well depicted, and
branch-duct type IPMT appears as a cluster of small cysts with or
Communication between the cysts and main pancreatic duct can often
be visualized, which may help in differentiation from a pseudocyst.
Intraductal papillary mucinous tumor has variable malignant
potential. Findings that favor malignant IPMT include the presence
of filling defects or papillary projections within the dilated
pancreatic duct or cysts and dilatation of the main pancreatic duct
(>15 mm for main-duct type and any dilation for branch-duct
Solid and papillary epithelial neoplasms
Solid and papillary epithelial neoplasm of the pancreas is a
rare tumor that occurs mainly in women under 40 years of age. The
mass is usually large (>10 cm) and commonly exhibits cystic and
hemorrhagic degeneration from necrosis with a thick rim of soft
tissue. On T1-weighted images, the hemorrhagic component appears
and the soft-tissue rim enhances after administration of gadolinium
contrast (Figure 9).
Other cystic masses
Pancreatic pseudocyst is the most common cystic lesion in the
pancreas (Figure 10). It is a complication of pancreatitis, and is
often seen in association with changes of pancreatitis. Pancreatic
abscess is a rare complication of pancreatitis, and can occur
secondary to superinfection of pancreatic necrosis or pseudocyst
(Figure 11). True epithelial cysts are rare in the pancreas but may
occur in patients with polycystic kidney disease or von
Hippel-Lindau disease (Figure 12). As noted, islet cell tumors are
rarely cystic. Lymphoepithelial cyst (lymphangioma) is a rare
cystic tumor that is often indistinguishable from mucinous cystic
Common primary malignancies that can metastasize to the pancreas
include carcinoma of the lung, breast, and kidney, as well as
melanoma. Metastases may involve the pancreas via local invasion
from the peripancreatic lymph nodes. Typically, metastases are
hypointense on T1-weighted images, and hyperintense on T2-weighted
images compared with the surrounding pancreas. Metastases from
melanoma may be hyperintense on T1-weighted images due to the
paramagnetic properties of melanin.
After administration of gadolinium contrast, the enhancement
pattern of the metastatic lesion often simulates that of the
primary tumor. Metastasis from renal cell carcinoma is often
The diagnosis of acute pancreatitis is usually made clinically,
and MR is mainly performed to exclude complications, or, more
importantly, to find the cause of pancreatitis, such as
choledocholithiasis or pancreas divisum. MR
cholangiopancreatography is an essential sequence to look for
choledocholithiasis as a cause of acute pancreatitis.
On MR, the pancreas may appear normal or show subtle enlargement.
In more severe cases, the signal intensity of the pancreatic
parenchyma becomes heterogeneous on T1-weighted fat-suppressed
images and postcontrast GRE images in the pancreatic phase
secondary to edema. Pancreatic necrosis, an important prognostic
indicator, appears as a focal perfusion defect on postcontrast
In the case of hemorrhagic pancreatitis, fluid collections with a
hemorrhagic component are present in or around the pancreas. The
fluid collections are typically hyperintense on T1-weighted images
due to methemoglobin.
Morphological changes of chronic pancreatitis, which occur in
the late stage of the disease, include atrophy and pancreatic duct
dilatation. Pancreatic calcification is not usually visible on MR
unless it is severe. The signal changes if the pancreatic
parenchyma precedes the morphological changes in the early stage of
the disease, which include decreased signal on both T1- and
T2-weighted images and heterogeneous enhancement secondary to
As already noted, the chronic pancreatitis can be focal and may
mimic pancreatic carcinoma (Figure 13). MR pancreatography
performed before and after secretin administration has been
investigated to assess exocrine function reserve in chronic
Mangafodipir trisodium (MnDPDP) (Teslascan, Amersham Health,
Princeton, NJ) is a T1-shortening contrast agent (hyperintense on
T1-weighted images) due to the paramagnetic nature of manganese. It
was originally developed as a liver-specific contrast agent, but
the agent is also taken up by normal pancreas. The signal intensity
of normal pancreatic tissue increases while the signal intensity of
pancreatic lesions remains the same, thereby increasing lesion
conspicuity on T1-weighted images.
Although the contrast-to-noise ratio is lower than on the images
acquired with gadolinium-based contrast agents, the temporal window
for imaging is longer since the washout of the MnDPDP takes more
than 1 hour. The clinical role of MnDPDP in the evaluation of
pancreatic disease has yet to be established.
Pancreatic MRI is primarily used as a problem-solving tool or
when CT is contraindicated. Recently, MR has been used more often
as a primary diagnostic modality. MRI has similar accuracy to CT in
detecting and staging of pancreatic tumors, and MR may have an
added role in characterizing lesions.