Computed tomography plays a primary role in the diagnosis and imaging workup of patients with pancreatic diseases. However, advanced magnetic resonance imaging (MRI) techniques offer images of the pancreas with excellent contrast resolution in a reasonable examination time. This article addresses the current techniques, the main indications, and the imaging features of common pancreatic diseases using state-of-the-art MRI.
is a Clinical Fellow, Division of Abdominal Imaging and
Intervention, Department of Radiology, Brigham and Women's
Hospital-Harvard Medical School, Boston, MA.
is the Associate Director, Division of Abdominal Imaging and
Intervention, and the Director, Abdominal and Pelvic MRI, Brigham
and Women's Hospital, and an Associate Professor of Radiology,
Harvard Medical School.
is a Research Fellow, Division of Abdominal Imaging and
Intervention, Brigham and Women's Hospital-Harvard Medical
is a Professor of Radiology, Harvard Medical School; and the
Executive Vice Chairman and Associate Radiologist-in-Chief,
Department of Radiology, Brigham and Women's Hospital.
Currently, magnetic resonance imaging (MRI) plays a secondary
role in the diagnosis and imaging workup of patients with
pancreatic diseases, when compared with multidetector-row computed
tomography (MDCT). However, technical innovations in MRI, such as
the development of phased-array multicoils, enhanced gradients, and
methods to reduce motion-related artifacts, allow us to obtain
images of the pancreas with excellent contrast resolution in a
reasonable examination time. Furthermore, the evaluation of the
pancreas can be optimized by the use of MR pancreatography (MRP),
which depicts the pancreatic ductal system, and with MR angiography
(MRA), which visualizes the peripancreatic vessels. At present,
this "all-in-one" approach, combining pancreatic parenchymal MRI,
MRP, and MRA, is presumably the most cost-effective imaging
technique in the evaluation of pancreatic diseases.
This article addresses the current techniques, the main
indications, and the imaging features of common pancreatic diseases
using state-of-the-art MRI.
To evaluate pancreatic lesions accurately, the use of multiple
pulse sequences that provide complementary information is required,
and, in general, a combination of T1-weighted (T1W) and T2-weighted
(T2W) sequences is obtained. In the ideal MRI sequence, the spatial
resolution is maximized within a short acquisition time while the
signal-to-noise ratio is maintained sufficiently high. The
development of surface coils oriented to image a specific volume of
the body (phased-array surface multicoil system or torso coil)
proved to be an important tool that improves the diagnostic value
of the individual pulse sequences and produces higher-resolution
images compared with the whole-volume body coil.
T1-weighted imaging that uses conventional spin-echo (SE)
technique requires significant imaging time and is no longer
Instead, we use breath-hold T1W spoiled gradient recalled echo
These sequences generate an echo by gradient reversal, allowing a
short echo time (TE) and, consequently, a much faster sequence.
For these, the flip angle should be ≥70˚, which is adequate to
obtain appropriate T1 contrast (demonstrated by higher signal
intensity from the liver than from the spleen); the echo delay time
should be <5 msec; and the repetition time (TR) should be
sufficient to image the entire pancreas in a multislice acquisition
(usually >100 msec).
These spoiled gradient images (eg, fast low-angle shot [FLASH],
multiplanar gradient-recalled [MPGR]) can be obtained with and
without fat suppression.
The normal pancreas has the highest signal intensity of the
intra-abdominal organs on fat-suppressed T1W images (Figure 1).
This is attributed to the larger amount of aqueous protein within
the glandular elements, an abundance of endoplasmatic reticulum of
the protein-producing acinar cells, and the high content of
paramagnetic ions, such as manganese, within the pancreas.
In elderly patients, this high T1 signal intensity may be reduced
in comparison with the signal intensity of the liver, most likely
because of age-related fibrosis.
The most common pancreatic diseases (ie, pancreatitis and
pancreatic adenocarcinoma) have longer T1 because of increased free
water protons and, therefore, have lower signal intensity compared
with that of the surrounding normal pancreatic parenchyma.
It has been shown that the conspicuity of pancreatic tumors and the
delineation of the pancreas from surrounding fat are best
established on fat-suppressed T1W images.
T2-weighted imaging is performed with a longer TR and TE (ie, TR
>1800 msec, and at least one echo with a TE ≥60 msec) when
compared with T1W sequences.
T2 images are achieved either by conventional SE, fast SE, or GRE
imaging. Images obtained with conventional SE pulse sequences take
longer and are prone to motion artifacts; thus, supplementary
techniques, such as fat suppression, are manda-tory.
Unlike conventional SE technique, fast SE (FSE) or turbo SE (TSE)
imaging can be performed in significantly less time, in 1 or 2
Fast or turbo spin-echo sequences are at least equivalent to
conventional SE sequences for abdominal lesion detection and
There are, however, important differences in image contrast between
fast and conventional T2W images.
Fat has higher signal intensity, and magnetic susceptibility
artifacts of iron and other metals are minimized on "fast" images,
compared with conventional SE images. As a consequence, using FSE
or TSE techniques is advantageous when imaging patients with
metallic stents, surgical clips, or embolization coils. However,
magnetization transfer is much greater on "fast" images and,
therefore, this effect may lower the signal intensity of solid
pancreatic neoplasms. Finally, because the phase-encoding signals
from shorter T2 tissues acquired at the end of the echo train have
low signal intensity, these tissues may be blurred on "fast"
Single-shot fast spin-echo (SSFSE) or half-Fourier acquisition
single-shot turbo spin-echo (HASTE) are sophisticated methods of
obtaining breath-hold T2W scans by acquiring approximately half of
the k-space in one long echo train after a single excitation.
The TR of these sequences is infinite. Some studies suggest that
such breath-hold sequences can replace conventional T2W images and
even "fast or turbo" SE images when appropriately optimized.
The major advantage of SSFSE or HASTE is that the individual images
are acquired in <1 second, allowing motion-free images in
patients, even without patient cooperation. Two disadvantages of
these sequences, when compared with conventional FSE or TSE,
include a lower signal-to-noise ratio (since fewer signals are
acquired) and significant blurring of tissues with shorter T2 (ie,
solid tissues) because of T2 decay during the long echo train.
Normal pancreatic parenchyma has a shorter T2 than most
abdominal organs and, therefore, exhibits low-to-intermediate
signal on T2W images (Figure 1).
The liver and, especially, the spleen have a longer T2 than the
pancreas and demonstrate normally higher signal intensity than the
pancreas on T2W images.
T1-weighted and T2W images through the pancreas should be
acquired axially, although examinations in other planes may be
useful in determining the organ of origin of a lesion or in
resolving potential problems with partial-volume artifact.
Field-of-view should be appropriate to the size of the patient.
Slice thickness should not be >8 mm, and there should be no more
than a half-slice gap between slices. In general, a slice thickness
of 4 to 5 mm is optimal for most applications.
Intravenous administration of extracellular contrast
The intravenous (IV) administration of an extracellular contrast
agent (gadolinium chelate) is a useful adjunct in the MRI
examination of the pancreas.
Theoretically, it is desirable to acquire images before and after
contrast administration using the same technique. Typically, these
are T1W images, which may be obtained with SE or, preferentially,
fat-suppressed GRE techniques, as described above. Preferably,
postgadolinium imaging is performed in different phases of
perfusion (Figure 1).
Administration of gadolinium chelates increases the differences
in signal intensity between normal pancreatic parenchyma and the
usually less vascular neoplastic tissue. Gadolinium-enhanced MRI is
also useful in evaluating acute pancreatitis, especially for the
detection of necrosis.
It can also help differentiate hypervascular pancreatic masses that
may simulate cystic lesions on noncontrast scans.
Magnetic resonance pancreatography
Magnetic resonance pancreatography typically employs "heavily"
T2W images of the pancreatic duct, in which pancreatic juices or
other stationary or slowly moving fluids appear hyperintense
relative to other abdominal tissues. Heavily T2W images are
breath-hold "fast" sequences with an extended TE (minimum TE of 160
Two different MRP "snapshot" techniques are usually applied:
Thin-section SSFSE or HASTE and thick-section rapid acquisition
with relaxation enhancement (RARE) (Figure 2).
MR pancreatography has several advantages over endoscopic
retrograde pancreatography (ERP): It is noninvasive, requires no
anesthesia, and does not use ionizing radiation. With MRP, there is
no increased risk of acute pancreatitis, and it can be performed on
patients with altered pancreaticobiliary anatomy following surgery
and in patients with complete obstruction of the ducts, in which
case it can also demonstrate the upstream anatomy and periductal
Magnetic resonance angiography
Currently, 3-dimensional gadolinium-enhanced magnetic resonance
angiography (3D Gd-MRA) is the best technique to evaluate the
peripancreatic vessels by MRI, especially in patients with
pancreatic neoplasm, to exclude arterial or venous invasion and to
diagnose anatomical vascular abnormalities or variants.
The signal obtained by 3D Gd-MRA is determined by the local
concentration of gadolinium in the vessels; therefore, acquisition
following an optimal time delay is mandatory. This approach also
enables one to calculate subtraction images that highlight venous
anatomy selectively, to remove disturbing high-intensity background
tissue, or to evaluate flow-patterns or organ perfusion.
Pancreatic MRI contrast media
Some specific pancreatic MRI contrast media are currently under
investigation, such as manganese dipyridoxyl diphosphate (MnDPDP).
A specific pancreatic contrast agent (previously used for liver
MRI), MnDPDP causes enhancement of the pancreas on T1W images (a
"positive" contrast agent).
Therefore, unenhanced pancreatic adenocarcinoma can be
differentiated from the normal-enhancing pancreas (Figure 3).
Although this seems to be especially useful in the diagnosis of
smaller tumors and in the differentiation between pancreatic
carcinomas and chronic pancreatitis, studies have shown that
MnDPDP-enhanced MRI seems to be less sensitive than spiral CT for
Therefore, the question remains whether the use of this agent
really improves the detection rate of pancreatic tumors.
Experimentally, target-specific MRI of pancreatic receptors
obtained by the administration of monocrystalline iron oxide
labeled with cholecystokinin has been evaluated.
However, additional studies are necessary to define their precise
role in pancreatic MRI.
The MRI protocol currently used at our institution for the
evaluation of the pancreas is summarized in Table 1.
Pancreatic MRI: Indications
The general indications for pancreatic MRI can be divided into 3
main categories: 1) suboptimal or equivocal CT or sonography
findings with a high clinical suspicion of pancreatic pathology; 2)
contraindications to iodinated contrast administration, including
contrast allergy history and renal failure; and 3)
contraindications to ionizing radiation (eg, pregnant women or
The specific indications for pancreatic MRI include the
following: Characterization of suspected parenchymal abnormalities
found on CT or ultrasound (US); detection and staging of
pan-creatic neoplasms as an adjunct to CT; characterization of
cystic pancreatic lesions; detection of small non-organ-deforming
pancreatic ductal adenocarcinomas; detection of endocrine tumors;
evaluation of acute and chronic pancreatitis when CT is not
diagnostic, especially to distinguish chronic pancreatitis from
neoplasm; detection of choledocholithiasis as a cause of acute
pancreatitis; detection of intraluminal pancreatic duct calculi;
and staging of chronic pancreatitis.
MRI of pancreatic neoplasms
Pancreatic tumors that originate primarily in the pancreas can
be epithelial or nonepithelial, can arise in the exocrine or
endocrine pancreas, can appear cystic or solid, or can be secondary
The triple role of MRI in evaluating pancreatic neoplasms is tumor
detection, characterization, and staging.
Ductal pancreatic adenocarcinoma
Ductal pancreatic adenocarcinoma accounts for approximately 90%
of all malignant pancreatic neoplasms.
Approximately 80% of the tumors occur in patients 60 to 80 years of
age, affecting men about twice as often as women.
In up to 70% of cases, the tumor is located within the pancreatic
Because of the close relationship of the pancreatic head to the
common bile duct and duodenum, pancreatic adenocarcinoma in the
head generally presents at an earlier stage than do tumors in the
pancreatic body or tail. At the time of clinical presentation, two
thirds of patients have an advanced tumor stage, with metastatic
disease present in 85% of cases.
As a distinct capsule does not confine the pancreas, invasion of
surrounding structures, especially peripancreatic vessels, is
Detection of pancreatic adenocarcinoma is based on unenhanced
T1W (fat-suppressed) images and pancreatic-phase postgadolinium T1W
spoiled GRE images.
On T1W (fat- suppressed) images, pancreatic cancer appears as a
low-signal-intensity mass (Figure 4A), and small tumors are clearly
separated from normal hyperintense pancreatic tissue.
Pancreatic ductal adenocarcinoma is typically a hypovascular lesion
(due to abundant desmoplasia) and appears as a low-signal-intensity
mass on T1W images during the pancreatic-phase after gadolinium
administration (Figure 4).
On T2W images, the tumor usually presents as an isointense or
hyperintense lesion (Figure 4). Secondary findings associated with
pancreatic adenocarcinoma are pancreatic duct dilatation (50%),
atrophy of the tail of the pancreas (20%), and dilated collateral
veins that suggest venous invasion. Postgadolinium breath-hold GRE
images are also important for the detection of hepatic metastases,
specifically during the portal venous phase.
Cystic epithelial pancreatic neoplasms
Cystic epithelial pancreatic neoplasms, such as serous cystic
tumors, mucinous cystic tumors, solid pseudopapillary tumors, and
intrapapillary mucinous neoplasms (IPMN) have distinctively
different MRI features when compared with pancreatic
Serous cystadenoma is generally considered to be a benign neoplasm,
with only sporadic reports of malignant degeneration.
It classically presents as a serous microcystic adenoma and, less
commonly, as an oligocystic (macrocystic) adenoma. Serous
microcystic adenomas represent 2% of all pancreatic neoplasms,
occur most frequently in elderly patients (mean age: 65 years), are
more common in women (70%), and have a propensity for occurrence in
the pancreatic head.
Although most serous cystic tumors are isolated lesions, an
association with von Hippel-Lindau disease does exist.
On pathology, a serous microcystic adenoma is a large (mean
diameter 6 cm) mass that consists predominantly of multiple (>6
cysts), small (<2 cm diameter) cysts that are divided by thin
septations. This well-circumscribed tumor is often lobulated and
contains a central, stellate, calcified scar. The presence of ≥6
small cysts within the mass is suggestive of serous cystic rather
than mucinous cystic neoplasm.
This tumor is typically not associated with pancreatic duct
dilatation or atrophy of the tail of the pancreas.
MRI shows the well-delineated contour of these tumors, the thin
septations, and their cystic components. Serous cystic tumors are
usually markedly hyperintense on T2W MRI, although some central
areas of low signal intensity may occasionally be seen that are
caused by the presence of a fibrous scar or calcification (Figure
On T1W MR images, the tumor is of low signal intensity, except in
cases in which hemorrhage is present.
The tumor is hypervascular, secondary to its rich subepithelial
Mucinous cystic tumors-
Mucinous cystic tumors range from tumors with malignant potential
to frankly malignant cystadenocarcinoma (ie, mucinous cystadenoma,
mucinous borderline tumor, and mucinous cystadenocarcinoma). The
mucinous macrocystic adenoma is a benign lesion, is more common in
women (90%), and usually presents in the 5th decade (mean age 45
years). Approximately 85% of these neoplasms arise in the tail or
body of the pancreas. Most typically, these solitary, large (mean
diameter 6 to 10 cm), hypovascular tumors are multilocular with
<6 individual cysts measuring >2 cm in size.
They contain mucin and usually have a thick wall, internal
septations, solid papillary excretions, and, occasionally,
MRI shows the unilocular (Figure 6) or multilocular nature of
this mass; scans obtained after IV administration of gadolinium may
show enhancement of the septations and the peripheral wall (Figure
MR images show the content of these cystic masses to be variable in
signal intensity; this variability is related to increased
proteinaceous content of the fluid.
Solid pseudopapillary tumor-
Solid pseudopapillary tumor (also called
solid and papillary epithelial neoplasm
papillary cystic tumor
) is a benign or low-grade malignancy that represents 1% to 2% of
all pancreatic tumors. They usually present in young women (mean
age 30 years) and do not show any race or location predilection.
This solitary, large (mean diameter 10 cm), well-demarcated mass
contains a capsule and is composed of both solid and cystic areas.
Internal hemorrhage, characterized by high T1 (Figure 7) and low T2
signal intensity (Figure 7), is a classic MR feature, as is a thick
solid capsule that enhances after contrast injection.
Intrapapillary mucinous neoplasm-
A relatively recent and increasingly reported entity, IPMN is
recognized more often now than it was previously probably because
of the increasing use of imaging modalities, such as CT and MRP.
This distinct mucin-producing tumor is thought to originate in the
main pancreatic duct or its side branches. When arising from a side
branch, they are most commonly located in the uncinate process.
They have either papillary hyperplastic, atypical, or malignant
epithelium that can cause local and vascular invasion and distant
They present at a mean age of 65 years and are slightly more common
in men (60%).
This tumor typically appears on MRI as a uni- or multilocular
cystic lesion (Figure 8) combined with a dilated main pancreatic
duct because of marked mucin secretion.
These tumors can be solitary, multiple, or diffuse sessile.
Communication between the main pancreatic duct and the cystic
lesion may be depicted, especially with MRP (Figure 8).
The most specific predictive signs of a malignant IPMN tumor are
the presence of a solid mass, main pancreatic duct dilatation
(>10 mm), diffuse or multifocal involvement, and attenuating or
calcified intraluminal content.
Acinar cell carcinoma and pancreatoblastoma-
Other epithelial exocrine pancreatic tumors, such as acinar cell
carcinoma and pancreatoblastoma, are very rare; however,
pancreatoblastoma is the most common pancreatic tumor in children.
Both tumors are more prevalent in males and present as a large
mass; acinar cell carcinoma presents at a mean age of 65 and
pancreatoblastoma at a mean of 4 years of age.
Endocrine pancreatic tumors
Endocrine pancreatic tumors, formally known as islet cell
tumors, are benign or malignant neoplasms with endocrine cell
They can be categorized into hyperfunctioning (insulinoma,
gastrinoma, glucagonoma, vipoma, and somatostatinoma) and
nonhyperfunctioning tumors that can be located in the pancreas or
peripancreatic tissue. They are uncommon tumors (1% to 2% of all
pancreatic tumors) that usually present in the 6th decade of life;
no significant difference in gender distribution has been reported.
Generally, endocrine tumors become clinically apparent because
of their hormone release and associated symptoms or because of
effects related to their size, especially with the
It can be difficult to assess malignancy in islet cell tumors.
While direct invasion by the tumor into adjacent organs and
metastases are macroscopic signs of malignancy, the only reliable
histologic marker is vascular invasion. The likelihood of
malignancy increases along with tumor size (93% of tumors >6 cm
are malignant), heterogeneity, multiplicity, and presence of
Insulinoma is the most common endocrine tumor of the pancreas. Its
clinical onset is typically associated with the Whipple triad
(starvation attack, hypoglycemia after a fasting period, and relief
by IV dextrose).
At the time of diagnosis, these tumors are usually (in ~90% of the
cases) solitary, small (<2.0 cm), intrapancreatic lesions. Local
invasion and distant metastases are present in 25% and 10% of
cases, respectively. Malignant insulinomas present with a larger
diameter (mean diameter6.2 cm). In only 5% to 10% of cases,
multiple insulinomas are found, and there is a slightly higher
incidence in the body and tail.
The classic findings of insulinoma are a solid, homogenous,
hypervascular mass, as detailed below.
Gastrinoma is the second most common endocrine tumor of the
pancreas. The clinical presentation is determined by excessive
gastrin production, which induces hypersecretion of gastric acid,
followed by peptic ulcerations and diarrhea (Zollinger-Ellison
syndrome). This typically small tumor (range 1 to 4 cm) occurs in
up to 90% of cases within the "gastrinoma triangle" (superior
margin-junction of the cystic and common bile duct; inferior
margin-second and third part of the duodenum; medial
margin-junction between head and body of the pancreas).
Forty percent of gastrinomas are located outside the pancreas, and
distant metastases are detected in 25% of cases at the time of
diagnosis. Gastrinoma usually presents as a solid homogenous
lesion; associated calcification is present in 20% of the
Glucagonomas are uncommon endocrine pancreatic tumors that are
almost always located in the pancreas and associated with local
invasion and distant metastases in 40% and 55% of the cases,
Glucagonoma syndrome includes necrolytic migratory erythema,
stomatitis, angular cheilitis, glossitis, diabetes mellitus,
anemia, achlorhydria, weight loss, and hypercoagulability. The
tumors are found predominantly in the pancreatic body and tail and
tend to be larger (mean diameter 6 cm) than insulinomas or
gastrinomas. Fifty percent of cases present as solitary,
heterogeneous, cystic lesions.
Up to 8% of hyperfunctional pancreatic tumors are vipomas, of which
60% are malignant.
These tumors are characterized by the secretion of vasoactive
intestinal peptide, which produces the Verner-Morrison syndrome
(watery diarrhea, hypokalemia, achlorhydria). These tumors occur
mostly in the pancreatic body and tail, with diameters ranging
between 4 and 10 cm.
Somatostatinoma is the most rare endocrine pancreatic tumor
(<1%) and, at the time of diagnosis, most are malignant (75%).
The clinical symptoms are related to the complex effects of the
suppression of growth hormone, thyroid-stimulating hormone,
insulin, glucagon, gastric acid, pepsin, and secretin. As a result,
the patients present with diabetes mellitus, gallstones, low
gastric output, and weight loss.
Nonhyperfunctioning endocrine tumors-
As a group, nonhyperfunctioning endocrine tumors are the third most
common islet cell neoplasms, accounting for about 15% of all
endocrine pancreatic tumors.
They usually cause no symptoms until patients present with stomach
or biliary tract obstruction. At that time, 90% of the tumors are
malignant, and distant metastases and local invasion are present in
25% and 50% of the cases, respectively. Because of their large size
(diameter >10 cm in 30% of cases), the tumors tend to necrose
The challenge that cross-sectional imaging faces today is to
identify small hyperfunctioning tumors and to stage large
hyperfunctioning and nonhyperfunctioning tumors for malignancy.
Since the majority of hyperfunctioning islet cell tumors are very
small, frequently measuring <3 cm in size, this can be a
difficult task. Islet cell tumors present as hypervascular lesions,
best seen in the early phases of pancreatic enhance-
The most striking evidence of malignancy is evidence of metastatic
disease to the liver or local lymph nodes. In contrast to ductal
adenocarcinoma, vascular encasement is usually not seen
On MRI, insulinomas and gastrinomas appear as lesions with low
signal intensity on T1WI (Figure 9) and high signal intensity on
T2WI (Figure 9).
Fat-suppression sequences are useful in emphasizing the signal
intensity differences between tumor and normal hyperintense
The use of IV gadolinium-DTPA is helpful, particularly in the
detection of islet cell tumors, since they are hypervascular
Ringlike enhancement in the periphery of the tumor is frequently
seen, while the center may remain hypointense secondary to
fibrosis. The more uncommon but generally larger hyperfunctioning
(eg, glucagonoma, vipoma, somatostatinoma) and nonhyperfunctioning
tumors present with a slightly lower signal intensity on T1WI and a
moderate signal intensity on T2WI.
Contrast administration will reveal an enhancement pattern similar
to that of the smaller insulinomas or gastrinomas. In large tumors,
hemorrhage or necrosis may occur and each is easily depicted.
Nonepithelial tumors such as lymphoma, teratoma, lymphangioma,
lipoma, and neural tumors can occur in the pancreas. Lymphoma can
cause multiple or solitary lesions that are associated with
adenopathy and advanced systemic involvement (Figure 10).
Metastatic disease can also spread to the pancreas, most often from
primary renal, lung, or breast cancer, as well as melanoma.
Metastases typically occur in the presence of advanced metastatic
MRI in pancreatitis
The role of radiologic imaging in patients with suspected
pancreatitis is to help confirm the diagnosis, try to establish the
cause of the disease, assess the severity, and detect
Acute pancreatitis is an acute inflammatory process of the
pancreas, with variable involvement of other regional tissues or
remote organs systems.
The 3 main causes include cholelithiasis (38%), alcoholism (35%),
and idiopathic etiologies.
On pathology, pancreatitis can be classified as mild (edematous
gland and/or spotty peripancreatic fatty tissue necrosis) or severe
(alternating chalky white fat necrosis and hemorrhage and/or
pancreatic necrosis). CT is the modality of choice in acute
pancreatitis evaluation due to its accuracy, reproducibility, and
In the assessment of acute pancreatitis, MRI can evenly depict
the presence and extent of necrosis and peripancreatic fluid
collections and is superior to CT in the detection of mild acute
A routine pancreas protocol including T2WI, fat-suppressed T1WI,
and a series of T1WI GRE sequences prior to and immediately
following gadolinium administration is a reliable means of staging
acute pancreatitis and reaching a prognosis.
In severe acute pancreatitis, gadolinium-enhanced MRI is
particularly useful for the assessment of pancreatic parenchymal
perfusion and the presence of necrosis. The enlargement of the
gland is well visualized on any sequence, and parenchymal edema is
better shown on unenhanced T1WI (Figure 11). T2-weighted sequences
are the most sensitive in revealing fluid collections. Furthermore,
by using additional MRP or MRA, MRI allows the accurate diagnosis
of underlying etiologies, such as choledocholithiasis or pancreas
divisum, and vascular complications.
Chronic pancreatitis is an irreversible clinical disorder
represented on pathology by irregular fibrosis and cellular
infiltration, ductal abnormalities, and loss of exocrine and
endocrine pancreatic function.
MRI examination should include T1W and T2W images and MRP. Chronic
pancreatitis presents with decreased T1 and variable T2 signal
intensity. The enhancement after gadolinium administration is
reduced and delayed. With MRP, the extent of morphologic ductal
changes as well as the severity of the disease can be assessed and
classified into 4 categories: Equivocal (<3 abnormal side
branches); mild (at least 3 abnormal side branches); moderate (main
pancreatic duct changes); and marked (main pancreatic duct with
severe dilatation of >1 cm, marked mural irregularity,
obstruction, or intraductal filling defects) (Figure 12).
Several centers have investigated functional MR evaluation of
the pancreas by obtaining MRP images before and after IV secretin
administration. After slow IV administration, secretin will
stimulate the secretion of fluid and bicarbonate by the exocrine
pancreas and increase the tonus of the sphincter of Oddi, thus
improving the visualization of the pancreatic duct and its side
Furthermore, the volume of effluent into the duodenal lumen can be
graded, allowing a relative estimation of the exocrine reserve.
Currently, the main indications for functional imaging are the
characterization of filling defects, the assessment of exocrine
function in the presence of parenchyma atrophy, and a better
evaluation of the papillary region.
An area of difficulty for all imaging modalities has been
differentiating focal pancreatitis from pancreatic adenocarcinoma.
Both types of lesions occur most often in the pancreatic head, may
cause bile duct obstruction, and may present in the absence of
calcification and duct strictures or dilatation.
However, patients with an inflammatory mass are likely to be
younger at the time of presentation and have a history of
alcoholism and previous episodes of acute or chronic pancreatitis.
Several studies have suggested that MRI can help differentiate
these 2 pathologies, especially with respect to focal or diffuse
changes in signal intensity and contrast enhancement. On
fat-suppressed T1WI, areas of chronic pancreatitis show diminished
signal intensity compared with normal pancreas but the degree of
signal reduction is usually less than that associated with
Inflammatory masses in chronic pancreatitis may result in signal
intensities comparable with those of the liver, whereas carcinoma
often shows signal intensities hypointense to the liver.
The "duct penetrating sign" on MRP images-a smoothly stenotic or
normal main pancreatic duct penetrating into a mass-has been
reported to occur more frequently in inflammatory pancreatic masses
than in pancreatic carcinoma.
Further study, however, showed that MRI could not reliably
differentiate the 2 conditions.
The use of MnDPDP may offer the potential to distinguish pancreatic
carcinoma from chronic focal pancreatitis, but further studies are
Autoimmune pancreatitis is a special form of chronic
pancreatitis that is unique in its effective clinical response to
On MRI, it presents as a diffuse or focal pancreatic enlargement
associated with narrowing of the main pancreatic duct and decreased
and increased signal intensity on T1W and T2W sequences,
In addition, contrast-enhanced imaging may show a peripancreatic
rim of decreased enhancement surrounding the pancreas and the
common bile duct on the arterial phase images.
MRI plays a triple role in the evaluation of the pancreas:
Diagnosis, staging, and detection of complications. The role of MRI
has increased, especially in imaging patients with suspected
pancreatic neoplasms. Currently, major MRI indications include
assessment of neoplasms (especially cystic pancreatic tumors) and
evaluation of chronic pancreatitis.
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