<strong>Secretin</strong>-<strong>Enhanced</strong> <strong>MRCP</strong>ables a more thorough evaluation <strong>of</strong> chronicpancreatitis <strong>and</strong> exp<strong>and</strong>s the horizon <strong>of</strong> thistest to other pancreatic abnormalities. Thisimproves on ERCP <strong>and</strong> EUS, which evaluateonly the morphologic changes. In this article,we will discuss the technique <strong>and</strong> indications<strong>of</strong> secretin-enhanced <strong>MRCP</strong> <strong>and</strong> present theresults <strong>of</strong> a study performed for the quantification<strong>of</strong> pancreatic exocrine function withsecretin-enhanced <strong>MRCP</strong> in patients withsuspected chronic pancreatitis.<strong>Secretin</strong>-<strong>Enhanced</strong> <strong>MRCP</strong>: <strong>Technique</strong>,<strong>Application</strong>s, <strong>and</strong> Quantification<strong>Secretin</strong><strong>Secretin</strong> is a gastrointestinal peptide thatstimulates pancreatic duct epithelial cellsto produce a bicarbonate-rich fluid. Physiologicgastrointestinal actions <strong>of</strong> secretin includeinhibition <strong>of</strong> gastric acid secretion <strong>and</strong>decreasing intestinal motility [5]. Production<strong>of</strong> biologically derived porcine secretin,which was used for pancreatic stimulationtests, ceased in 1999. Synthetic forms <strong>of</strong>both porcine <strong>and</strong> human secretin (ChiRho-Stim, ChiRhoClin <strong>and</strong> SecreFlo, Repligen)are now available. All three forms—that is,biologic, synthetic porcine, <strong>and</strong> synthetic humansecretin—have been shown to be equivalent<strong>and</strong> can be used interchangeably [6].The adverse effects <strong>of</strong> secretin are mainlynausea, flushing, abdominal pain, <strong>and</strong> vomiting<strong>and</strong> can be seen in up to 5% <strong>of</strong> patients.Acute pancreatitis is listed as a contraindicationto secretin administration (package insert,ChiRhoClin). However, some institutions injectsecretin before resolution <strong>of</strong> acute episodeswithout reported major adverse effects [7, 8].<strong>Secretin</strong>-<strong>Enhanced</strong> <strong>MRCP</strong> <strong>Technique</strong>The MRI protocol used for secretinenhanced<strong>MRCP</strong>, which is the functionalevaluation <strong>of</strong> the pancreas, can be performedalone or in combination with a st<strong>and</strong>ard pancreasprotocol. At our institution, patients referredfor their first secretin-enhanced <strong>MRCP</strong>who have never had a pancreatic MR evaluationusually undergo an examination in whichthe st<strong>and</strong>ard pancreas protocol is combinedwith the secretin-enhanced <strong>MRCP</strong> protocolto evaluate both pancreatic morphology <strong>and</strong>function. In this article, we describe the sequencesused only for the secretin-enhanced<strong>MRCP</strong> portion <strong>of</strong> the protocol.Patient PreparationA superparamagnetic iron oxide–containingoral MR contrast agent (such as ferumox-Fig. 1—32-year-old woman imaged withoutadministration <strong>of</strong> oral ferumoxsil. MR image showspreexisting T2 bright natural duodenal secretions(arrows).sil, [Gastromark, Covidien]) is administeredorally before the examination. Two bottles,300 mL each, are administered 30 minutes <strong>and</strong>just before the examination. This T2-shorteningnegative enteric contrast agent mixes withthe preexisting T2 bright gastric <strong>and</strong> duodenalfluid, essentially eliminating its T2 signal. T2bright pancreatic fluid subsequently secreted inresponse to secretin can be easily identified onthis T2 dark background (Figs. 1 <strong>and</strong> 2). Naturallyoccurring negative oral contrast can beobtained from blueberry <strong>and</strong> pineapple juices<strong>and</strong> may be used as a lower cost alternative t<strong>of</strong>erumoxsil for qualitative evaluation [9]. Thesejuices have a natural high manganese contentthat makes them paramagnetic <strong>and</strong> thereforedark on T2 imaging.Sequences<strong>Secretin</strong>-enhanced <strong>MRCP</strong> were performedusing 1.5-T systems at our institute. After obtainingscout images, axial <strong>and</strong> coronal T2-weighted HASTE images through the abdo-TABLE 1: Typical Sequence ParametersFig. 2—50-year-old woman imaged with oralferumoxsil administration. MR image shows T2 darkfluid (ferumoxsil) in stomach <strong>and</strong> duodenum (arrows).men are obtained. Table 1 contains typicalsecretin-enhanced <strong>MRCP</strong> parameters.An initial breath-hold thick oblique coronalfat-suppressed heavily T2-weighted long-TE HASTE image encompassing the pancreas<strong>and</strong> duodenum is acquired <strong>and</strong> assessedfor position. After an IV test dose <strong>of</strong> 0.2 μg <strong>of</strong>human secretin (ChiRhoStim), 0.2 μg/kg <strong>of</strong>the same is administered over 1 minute withthe patient in the gantry <strong>and</strong> the breath-holdoblique coronal heavily T2-weighted fatsuppressedlong-TE HASTE sequence (thickslab <strong>MRCP</strong> sequence) is repeated every 30seconds for 10 minutes. A slice thickness <strong>of</strong>60 mm is used so that the entire pancreas <strong>and</strong>duodenum are included. When these 20 imagesare viewed sequentially, they provide adynamic assessment <strong>of</strong> pancreatic exocrinefunction in response to secretin (Fig. 3).At the end <strong>of</strong> the 10-minute dynamic assessment,another set <strong>of</strong> axial <strong>and</strong> coronal HASTEimages is obtained through the abdomen. Thisset <strong>of</strong> images allows estimation <strong>of</strong> the totalSequence HASTE Long TE HASTETR (ms) Infinite 3000Time between slice acquisition (ms) 1050 3000TE (ms) 72 972Matrix256 x 176 (axial)256 x 256256 x 256 (coronal)Slice thickness (mm) 4 60Acquisition 2D 2DFlip angle 180° 150°Slices Multislice Thick slabFOV (mm)350 x 240 (axial)200 x 200350 x 350 (coronal)Pixel b<strong>and</strong>width (Hz) 780 130AJR:198, January 2012 125
Sanyal et al.Fig. 3—35-year-old woman with normal pancreatic function. Three selected images after secretin injection <strong>of</strong> 20 sequential heavily T2-weighted long TE HASTE imagesobtained over 10 minutes show normal filling <strong>of</strong> duodenum, which progresses past genu.AFig. 4—43-year-old man with normal pancreatic function.A, Presecretin coronal HASTE image shows collapsed duodenum with minimal T2 dark ferumoxsil (arrows).B, Postsecretin coronal HASTE image shows duodenum distended with new T2 bright fluid (arrows), indicatingnormal exocrine function.BFig. 5—55-year-old man with established chronicpancreatitis. MR image obtained 5 minutes aftersecretin injection shows dilated irregular mainpancreatic duct with loss <strong>of</strong> normal tapering. Sidebranch ectasia is present.Fig. 6—52-year-old man with chronic pancreatitis <strong>and</strong> transient side branch dilation. Image obtained 30 seconds after secretin injection (left) does not show significantside branch dilation. Image obtained at 3 minutes (center) shows transient filling <strong>of</strong> dilated side branches with T2 bright fluid (arrow), which becomes much less apparent on5-minute image (right). Note volume <strong>of</strong> secretion is also reduced with only partial filling <strong>of</strong> bulb.amount <strong>of</strong> T2 bright fluid secreted into the duodenumin response to secretin (Fig. 4) as wellas assessment <strong>of</strong> changes in duct morphology.Chronic Pancreatitis <strong>and</strong> <strong>Secretin</strong>-<strong>Enhanced</strong> <strong>MRCP</strong>In chronic pancreatitis, fibrous tissue graduallyreplaces the gl<strong>and</strong>ular elements in thepancreas. This process is reflected in secretinenhanced<strong>MRCP</strong> by characteristic changes inthe main pancreatic duct (MPD), side branches,<strong>and</strong> volume <strong>of</strong> pancreatic secretion [10].Ductal ChangesERCP has been considered a radiologic referencest<strong>and</strong>ard because <strong>of</strong> its ability to detectmild ductal changes <strong>of</strong> chronic pancreatitis.During ERCP, injection <strong>of</strong> contrast materialunder pressure causes overdistention <strong>of</strong> theductal system [11]. In comparison with thistechnique, administration <strong>of</strong> secretin in secretin-enhanced<strong>MRCP</strong> creates a more physiologicductal distention. Because <strong>of</strong> lower spatialresolution <strong>and</strong> lack <strong>of</strong> overdistention, secretin-enhanced<strong>MRCP</strong> cannot match the subtleductal abnormalities identified on ERCP. However,ductal distention by T2 bright fluid after126 AJR:198, January 2012
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