الفهرس 
Anatomy Of The Pancreas
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Abstract
This essay evaluates the role of MRI in imaging all types of acute
and chronic pancreatitis, pancreatitis complications, and other
important differential diagnoses that may mimic pancreatitis.
MRI is a valuable alternative modality, with better diagnostic
outcome than CT for the diagnosis and follow-up of acute and
chronic pancreatitis.
Advantages of using MRI in pancreatitis
1. MRI is a non-ionizing cross sectional imaging modality with a
safer intravenous contrast agent. This is essentially important
in patients with acute pancreatitis, who may have a
concomitant renal impairment of some degree and usually
require repeated follow-up imaging.
2. MRI is useful in patients who have contraindications to use
iodinated contrast agents.
3. MRI offers higher sensitivity than CT for the diagnosis of
subtle early changes of acute pancreatitis (i.e., interstitial
pancreatitis and peripancreatic edema).
4. It is more accurate than CT in detecting some local
complications of acute pancreatitis such as hemorrhage,
necrotic collections and complicated pseudocysts.
5. MRCP is a non invasive method for imaging of the ductal
system. 6. Unlike ERCP, MRCP can show the dilated duct upstream from
an obstructing stone.
7. MRI is more sensitive than CT in detection of parenchymal
changes in chronic pancreatitis.
8. It is more sensitive than CT in detecting stones surrounded by
fluid.
9. It provides characteristic signs for some rare types of chronic
pancreatitis such as autoimmune, hereditary and groove
pancreatitis.
Disadvantages and limitations of using MRI in pancreatitis.
1. It requires patient cooperation and breath holding, otherwise,
there can be motion artifacts that affect the visualization of the
pancreas and its adjacent structures. However, the recent
development of new respiratory gating techniques and motion
resistant pulse sequences can overcome this problem
especially in acutely ill patients unable to breath hold.
2. MRI is time-consuming and relatively expensive with
comparison to US or CT.
3. Using MRI contrast media in patients with severe acute
pancreatitis associated with renal insufficiency has the
potential danger of developing nephrogenic systemic fibrosis.
4. On MRCP, pancreatic duct visibility can be decreased by the
overlap of fluid-containing organs (e.g. stomach and
duodenum).5. It is less sensitive than CT in detecting gas (in abscess),
calcifications and small intraductal stones not surrounded by
fluid.
The routine MRI sequences for pancreatitis require the combined
use of T1-weighted, T2-weighted sequences, and MRCP, in addition
to dynamic contrast-enhanced imaging which gives a comprehensive
assessment of the extent of necrosis and full range of inflammatory
process extension.
MRI evaluation of chronic pancreatitis allows for the visualization
of parenchymal signal changes on T1-weighted fat-suppressed
images and the visualization of arterial contrast enhancement
patterns on serial contrast enhanced images as well as measurement
of pancreatic size.
Ductal changes shown on static images and changes evident by
secretin-stimulated MRCP can indirectly detect the degree of
parenchymal fibrosis and severity of the disease.
Evaluation of pancreatic exocrine function by grading duodenal
filling during the same session provides additional information about
the functional condition of the gland.
When diffusion weighted imaging is combined with conventional
MR imaging, it provides important information in the detection and characterization of a variety of pancreatic abnormalities, including
acute and chronic pancreatitis