Magnetic Resonance Cholangiopancreatography-Techniques and Applications

Magnetic Resonance Cholangiopancreatography : Techniques and Applications Sudha A Anupindi, MDa,b,*,TeresaVictoria, MDa,b KEYWORDS  Magnetic resonance cholangiopancreatography  Children  Biliary disease  Pancreas  T  1.5 T contrast agents Since its introduction in 1991, MRCP has become an invaluable tool in the imaging evaluation of the biliary system This article reviews MRCP techniques and their applications for assessing anatomic biliary and pancreatic variants and common pediatric diseases TECHNIQUE Conventional Techniques for Imaging Pancreaticobiliary System The basic technique of MRCP for evaluating the biliary tree uses heavily T2 weighted sequences, because bile has a high water content and appears bright on these sequences with its long T2 relaxation times, in contradistinction to the surrounding solid organs, which are relatively dark.1,2 The conventional protocols for MRCP include thick-slab T2 weighted turbo spin echo (TSE) and half-Fourier acquisition single-shot turbo spin echo (HASTE) in the coronal, coronal oblique, and axial planes Heavily T2 weighted sequences can be acquired in a single thick slab (30 to 80 mm thickness) in any plane and can be performed without postprocessing techniques The advantage of multiplanar imaging, particularly in coronal and oblique planes, is improved visualization of overlapping fluid structures.3–6 The advantage of HASTE is the acquisition of thin slices (3 to mm) rapidly with minimum patient motion If a patient is sedated or cannot breath-hold, these sequences can be performed with a Department of Radiology, The Children’s Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104, USA b University of Pennsylvania School of Medicine, Philadelphia, PA, USA * Corresponding author Department of Radiology, The Children’s Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA 19104 E-mail address: anupindi@email.chop.edu (S.A Anupindi) Magn Reson Imaging Clin N Am 16 (2008) 453–466 doi:10.1016/j.mric.2008.04.005 1064-9689/08/$ – see front matter ª 2008 Elsevier Inc All rights reserved mri.theclinics.com The imaging techniques currently advocated for the evaluation of pancreatic and biliary diseases in children include sonography, hepatobiliary scintigraphy, CT and magnetic resonance cholangiopancreatography (MRCP) Imaging of the pancreas and biliary system often requires a combination of two or more of these modalities to reach an accurate diagnosis Among these techniques, ultrasonography (US) remains the screening examination of choice in a child of any age presenting with symptoms suggesting a primary pancreaticobiliary process US can provide a rapid assessment of biliary tree and pancreas, but it may be limited in providing anatomic detail in certain areas, and it cannot provide functional information Hepatobiliary scintigraphy offers physiologic information, but it lacks anatomic detail CT is the first line of imaging in adults who have pancreatic diseases, especially pancreatic masses With the concerns of ionizing radiation, however, CT is used cautiously for evaluating pancreaticobiliary abnormalities in children, with the exception of evaluation of acute trauma, complications of pancreatitis, and postsurgical findings Although once the reference standard for depicting biliary pathology, endoscopic retrograde cholangiography (ERCP) is not used often for diagnosis because of radiation exposure It has evolved to be mainly a therapeutic option MRCP has emerged as a fast, safe, accurate, noninvasive alternative to ERCP for evaluating the biliary system in children It depicts simultaneously the biliary tree and pancreatic parenchyma without using ionizing radiation or 454 Anupindi & Victoria respiratory triggering Acquisition of both thick collimation slab and thin collimation multislice images complement each other in the visualization of the biliary tree The thick slab image should be interpreted in conjunction with the thin slab axial and coronal images to avoid artifact from volume averaging Conventional unenhanced T1 and T2 weighted imaging also is performed routinely for evaluating the pancreaticobiliary system T1 and T2weighted images are necessary to assess extrahepatic causes of biliary obstruction and the liver parenchyma Patient Preparation Before Scanning Four hours before the study, the patient should have nothing by mouth (NPO) to decrease bowel motion Bowel paralytic agents are not used in the authors’ institution, nor have recent publications recommended this as part of their protocol Negative oral contrast agents that have superparamagnetic effects may improve the visualization of the biliary ducts by nulling the inherent high signal of gastric juices in the stomach and duodenum Commercially available negative oral contrast agents, such as ferumoxsil (Gastromark, Mallinckrodt, St Louis, MO), use the iron content to produce dark signal in the bowel.6 More palatable and less expensive alternatives, however, include pineapple or blueberry juice, which have high manganese content and have similar darkening effect on MR imaging.7 Coil selection is critical and depends on the patient size The smallest possible coil that covers a body part of interest should be used to ensure high signal-to-noise (SNR) and improve spatial resolution Contrast Agents MR images of the biliary system and pancreas are obtained routinely with conventional gadolinium chelate agents Gadolinium-enhanced T1 weighted images with fat saturation are helpful when evaluating hepatic parenchymal disease before and after liver transplant or neoplastic processes affecting the liver and bile ducts Delayed scanning 10 to 20 minutes after the intravenous administration of contrast agents results in bile becoming hyperintense.8–10 Conventional gadolinium chelates used presently are excreted renally and offer limited assessment of the biliary system and function On the other hand, newer contrast agents, such as manganese derivatives, mangafodipir trisodium (Teslascan, Amersham Biosciences, GE Healthcare Technologies, Chalfont, St Giles, United Kingdom); improved gadolinium chelates, such as gadobenate dimeglumine (Multihance, Bracco, Milan, Italy); and gadolinium-ethoxybenzyldiethylene-triamine-penta-acetic acid (Gd-EOBDPTA), which are taken up by the hepatocytes and excreted into the biliary system, have the potential to improve visualization of the hepatobiliary system.4,11 They have rigorous protocols and delivery systems, however, which limit their use in pediatric populations Teslascan is no longer available in the United States.5 Advanced Techniques: T MR Imaging Advanced techniques that improve SNR and decrease acquisition time include three-dimensional T2 weighted TSE techniques and imaging with 3T scanners.4,5,12 Maximum and minimum intensity projections reconstructed from three-dimensional T2 sequences performed with parallel acquisition technique allow for higher SNR, thinner slices without gaps, and overall improved anatomic accuracy.4 The advantage of this technique in children is more diagnostic information with less scan time This is extremely beneficial from a sedation viewpoint Three-dimensional sequences can be performed with both 1.5 T and T magnets In addition, techniques such as VERSE (variablerate selective excitation) and SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) have been introduced in the last years for MRCP on both 1.5 T and T equipment.4,5 The goal of these sequences, in conjunction with parallel imaging, is again to shorten scan times and improve SNR and spatial resolution The technical parameters for T and 1.5 T scanners differ and need to be optimized for each scanner A T magnet has more inherent T1 characteristics Thus, the repetition time, flip angle, and inversion time need to be selected to achieve the desired signal in the tissue examined T2 is virtually unchanged or perhaps slightly decreased with an increase in magnetic field strength.13 Several publications have described the following advantages with T imaging: Superior visualization of the cystic duct and common bile duct (CBD) using HASTE and three-dimensional TSE sequences Increased sensitivity and specificity in the detection of intrahepatic ductal variants Improvement in radiologist’s confidence level in diagnosis Improved visualization of nondilated ducts6 This last point is important in children, because often they have very small nondilated ducts The existing data, however, not show that the pancreatic duct is evaluated better at T than at MR Cholangiopancreatography Techniques 1.5 T imaging.6 The disadvantages of T imaging include greater susceptibility artifacts At the present time, there are no dedicated studies comparing MRCP at T versus 1.5 T in children T MRCP imaging is promising for improving SNR and contrast-to-noise ratio Pitfalls in Diagnosis at Magnetic Resonance Cholangiopancreatography A major limitation of MRCP in children is the small size of the peripheral ducts, which can result in false-negative studies The use of both secretin (Figs and 2) and morphine sulfate has been described to overcome this obstacle Secretin is a hormone that stimulates the exocrine pancreas to secrete fluid and bicarbonate, resulting in a transient increase in pancreatic fluid volume that then distends the pancreatic duct.14,15 A negative oral contrast may be administered also to suppress the signal of the stomach and duodenum, which otherwise may interfere with the signal of the biliary duct Fukukura and Fujiyoshi14 reported visualization of the main pancreatic duct in the head, body, accessory pancreatic duct, and branch duct before the administration of secretin in 94%, 84%, 9%, and 1%, respectively Following the administration of secretin, each segment of the pancreas was visualized in 100%, 98%, 42%, and 18% respectively, allowing for a better evaluation Fig.1 Effect of secretin on the normal pancreatic duct (A) Normal appearance of the pancreatic duct before the administration of secretin Images at (B) and 10 (C) minutes following the administration of the hormone show improved visualization of the pancreatic duct and excretion of pancreatic juices into the duodenum (Courtesy of Ivan Pedrosa, MD, Boston, MA) 455 456 Anupindi & Victoria Fig Evaluation of pancreas divisum before and after administration of secretin (A) Before the administration of secretin, there is limited visualization of the pancreatic duct (arrows), particularly distally A possible cyst is present at the level of the pancreatic head (arrowhead) (B) Four minutes after administration of secretin, there is better visualization of the pancreatic duct, which drains into the minor ampulla (arrow) Communication of the dorsal duct with the cystic lesion is now evident In addition, a small ventral duct now is seen draining into the major ampulla (arrowhead) with no evidence of communication with the dorsal duct (Courtesy of Ivan Pedrosa, MD, Boston, MA.) of the smaller ducts Another publication has shown improved visualization of intraductal filling defects and ductal narrowing by overdistending the ducts with secretin.16 This finding was less apparent in patients with chronic pancreatitis who already had chronically dilated ducts These authors also demonstrated that congenital variants, such as pancreas divisum and associated anomalies including santoriniceles (a cystic dilatation of the dorsal duct just proximal to the minor papilla), were more evident after the administration of secretin.17 The use of secretin in the pediatric population has been shown to be safe and to significantly enhance visualization of the pancreatic duct.6 The drawback of secretin administration includes the cost of the hormone and the increased MR imaging scan time Its use, however, may obviate invasive procedures like ERCP Morphine sulfate, which is an opioid analgesic, also has been used to improve ductal visualization Morphine increases the contraction of the sphincter of Oddi, resulting in an increase in the resting biliary pressure and distension of the biliary and pancreatic ducts Silva and Friese18 have described the use of morphine during MRCP in adults to improve the visualization of small intrahepatic biliary and cystic ducts, and the main pancreatic duct A slow intravenous injection (over to minutes) of 0.04 mg/kg of morphine sulfate was given with a scan delay time of 10 to 20 minutes.18 The use of morphine appeared to be particularly helpful when evaluating the biliary anatomy before transplant However, at this time, there are no clear indications or published experience regarding the use of morphine enhanced MRCP in children Artifacts Artifacts can be classified as motion-related, technical, or miscellaneous Motion artifacts Artifacts secondary to motion are the result of tissue movement during the acquisition of the data and are categorized as voluntary or involuntary.19 A key element in optimizing MRCP is suppression of voluntary patient motion Voluntary motion is often the result of anxiety and claustrophobia, resulting in gross motion degrading the images Procedural sedation can minimize voluntary motion, and patients should be screened carefully before imaging to determine the need for sedation Usually children over years of age can cooperate successfully for MRCP after explanation of the procedure and reassurance by the parents In the authors’ experience, procedural sedation is essential for children younger than years It is also helpful to ensure that the patient is in a comfortable position and has an empty bladder Procedural sedation requires monitoring and can be achieved best using several agents, including but not limited to intravenous fentanyl citrate, versed, pentobarbital sodium, ketamine, and propofol.20 A complete discussion of the protocols for sedation is beyond the scope of this article, as they vary with institutional policies Involuntary motion-related artifacts result from breathing, motion from adjacent structures, such MR Cholangiopancreatography Techniques as bowel, and pulsation artifacts from vessels Respiratory triggering can minimize respiratoryrelated artifacts Respiratory motion artifact also may result in misregistration of the ducts, which can appear discontinuous or stenotic on maximal intensity projection (MIP) sequences Careful interpretation of the source images or use of single-section sequences may help avoid these problems Keeping the patient NPO to the study can help reduce bowel peristalsis Technical-related artifacts The disadvantage of conventional MRCP techniques, SSFSE, and HASTE is low signal-to-noise at the expense of resolution, which can impair visualization of small intrahepatic biliary radicals.4,21–23 The disadvantage of the thick-slab technique is impaired visualization of small intraductal filling defects because of volume averaging The limited number of projections with slab techniques also means that anatomic detail may be delineated poorly Overestimation of ductal narrowing may occur in MRCP when compared with ERCP.24 During ERCP, the ducts are overdistended because of the relatively high pressure injection of contrast In MRCP, the ducts are imaged in the in vivo state, sometimes artificially suggesting focal stenosis or narrowing A normal duct distal to area of narrowing suggests that narrowed area is in fact an artifact rather than a true finding MRCP imaging at T also has brought new challenges with regard to artifacts Radio frequency (RF) inhomogeneity is one of the greatest challenges of T imaging.5 The physics behind this artifact are beyond the scope of this article Suffice it to say that constructive or destructive interference from standing RF waves results in an area of brightening and darkening, respectively.13 The larger the field of view, such as in obese patients, the more pronounced the artifact A related artifact occurs with electrical current interference in a highly conductive medium like ascites, resulting in focal signal dropout Chemical shift artifact is also more apparent at T imaging This artifact is caused by difference between the RF of protons in water and fat, resulting in misregistration artifact only seen along the frequency-encoding axes This may be overcome by use of saturation pulses to null the signal of fat, or by swapping the frequency and phase-encoding direction.13 Miscellaneous artifacts Blood products, gas, and other debris in the bile ducts can decrease the signal intensity of bile and create pseudo lesions leading to false-positive results.4 Metallic artifacts from surgical clips or stents can also result in signal void and obscuration of pathology.23 The use of spin echo sequences instead of gradient echo, and avoidance of fat-suppressed sequences helps to decrease these artifacts Another artifact on MRCP is a pseudolesion related to adjacent arteries causing a flow artifact in a duct-mimicking stones.23 Such flow-related artifacts can be seen on MIPs, and a thorough evaluation of source images can overcome this pitfall The presence of iodinated material in the biliary tract from prior ERCP can appear as low signal intensity filling defect on heavily T2 weighted sequences, simulating pathology MRCP should not be obtained immediately after ERCP.23 A plain abdominal radiograph may aid in evaluating residual contrast in the biliary tree before obtaining an MRCP NORMAL ANATOMY AND VARIANTS By the fourth week of gestation, ventral and dorsal pouches develop at the junction of the foregut and the midgut (Fig 3) The ventral bud (or hepatic diverticulum) develops into the liver, gallbladder, ducts, and ventral aspect of the pancreas and their accompanying bile ducts, whereas the dorsal bud gives rise to the dorsal pancreas At about week of gestation, the dorsal and ventral anlagen of the pancreas fuse, and their ducts unite The main pancreatic duct is formed from the ventral duct and the distal aspect of the dorsal bud, draining in most cases through the major papilla into the duodenum The portion of pancreatic duct extending from the ampulla to the site of anastomosis of the dorsal and ventral pancreatic anlagen is referred to as the duct of Wirsung If a segment of the dorsal duct persists distal to the site of developmental anastomosis, this duct is termed the Santorini or accessory duct The caliber of the pancreatic duct increases slightly from the tail to the head of the pancreas In its course, the duct receives about 25 tributaries, which insert into the duct at right angles.25,26 These usually are not seen at MRCP unless they are pathologically or iatrogenically (by means of secretin) distended In 91% of the population, the main drainage route for the pancreas is through the duct of Wirsung, which joins the CBD at the major ampulla The accessory pancreatic duct or duct of Santorini may be present in up to 44% of the population and may drain through the minor papilla, located about cm cephalad from the major papilla.27 The ducts of Wirsung and Santorini can be seen on MRCP The right hepatic duct divides into anterior and posterior portions, which then join proximally 457 458 Anupindi & Victoria Fig Embryologic development of the pancreas and biliary tree (A, B) The ventral pancreatic bud and biliary tree arise from the hepatic diverticulum while the dorsal pancreatic bud arises from the dorsal mesogastrium (C, D) After clockwise rotation, the dorsal and ventral pancreatic anlagens fuse The main pancreatic duct drains by means of the ventral duct into the major papilla, while the dorsal duct drains the accessory pancreatic ducts through the minor papilla The right hepatic duct, which is usually shorter than the left, joins the left hepatic duct, and together they form the common hepatic duct (CHD) The cystic duct inserts into the CHD usually below the confluence of the right and left hepatic ducts to form the CBD The CBD should measure less than mm in neonates, less than mm in infants up to year of age, and less than mm in older children and adults In the postcholycystectomy patient, the CBD may measure up to cm.25,26 Knowledge of normal congenital variants is important for surgical planning Variants of the pancreatic system include an anomalous pancreaticobiliary junction, which has a prevalence of 1.5% to 3.2% of the population.26,28 In this variant, there is fusion of the pancreatic duct and CBD outside of the wall of the duodenum, forming a common channel that measures more than 1.5 cm in length The junction is distal to the sphincter of Oddi, allowing reflux of the pancreatic juices into the CBD This finding has been associated with the formation of type choledochal cyst, perhaps because of the weakening of the ductal wall by pancreatic enzymes, and with an increased incidence of pancreatitis, thought to be related to retrograde reflux of pancreatic juices into the anomalous duct Other pancreatic ductal variants include a dominant duct of Santorini and a variant called ansa pancreatica, in which the pancreatic duct forms a small loop at the embryologic site of anastomosis between the ventral and the dorsal duct.25 There are also numerous variations of the cystic duct that can contribute to biliary injury at surgery.29 CONGENITAL PANCREATIC ANOMALIES Pancreas Divisum In 6% to 8% of individuals, the ventral and dorsal pancreatic anlagens fail to fuse, resulting in a longer dorsal duct that drains by means of the minor ampulla, and a shorter, ventral duct that drains into the major ampulla, a congenital anomaly called pancreas divisum (Fig 4) Its significance is that the dorsal duct may not accommodate the flow of pancreatic secretions through the minor papilla MR Cholangiopancreatography Techniques Pancreas Agenesis or Hypoplasia Total pancreas agenesis is extremely rare and virtually incompatible with life Partial agenesis of the pancreas is usually caused by agenesis of the dorsal or ventral pancreatic anlage Dorsal agenesis is more common than ventral agenesis Patients may present with abdominal pain caused by pancreatitis or with diabetes mellitus from an insufficient excretion of insulin On imaging, dorsal agenesis may present as a foreshortened pancreas, or in the most extreme form, it appears as a rounded pancreatic head with nonvisualization of the remaining pancreatic tissue.26 Fig Pancreas divisum 15-year-old girl with acute pancreatitis Coronal maximal intensity projection acquired from three-dimensional T2 weighted image with SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) shows that the main pancreatic duct drains into the minor papilla while the common bile duct drains into the major papilla, findings diagnostic of pancreas divisum It is equivocal whether this entity truly causes pancreatitis MRCP and secretin-enhanced MRCP are highly sensitive and specific in detecting pancreas divisum,2,6,17,30 as illustrated in Fig Annular Pancreas Annular pancreas is the second most common congenital anomaly of the pancreas, after pancreatic divisum It may occur as an isolated finding, or it can be associated with other congenital anomalies including tracheoesophageal fistula, duodenal atresia or stenosis, esophageal atresia, and Down syndrome In this anomaly, which occurs at a rate of of every 2000 births, the pancreatic tissue completely or partially encircles the second part of the duodenum, resulting in gastric outlet obstruction If the tissue completely surrounds the pancreas, the obstruction is complete, and the patient usually presents at infancy If there is partial encirclement, the patient may become symptomatic later in life, or the finding may be detected incidentally on imaging studies Embryologically, annular pancreas is thought to be caused by a bifid ventral anlagen, which surrounds the duodenum and then fuses with the dorsal pancreatic portion forming a ring around the duodenum.26 On MR imaging, an annular pancreas appears as high signal tissue on fat-suppressed T1 weighted sequences, completely or partially encircling the duodenum.6 CONGENITAL BILIARY ANOMALIES Biliary Atresia Biliary atresia is thought to be the sequela of a destructive inflammatory process leading to ductal fibrosis.31 It may be focal, intrahepatic, or extrahepatic The focal and intrahepatic types are extremely rare and thought to be caused by an intrauterine vascular insult The most common form is extrahepatic atresia (Fig 5) Extrahepatic biliary atresia usually becomes symptomatic in the first days or months of life as jaundice Prompt diagnosis is imperative, as the prognosis decreases proportionally with increasing age Several studies have evaluated the utility of MRCP evaluating the biliary ducts in infants.32 MRCP may be useful when findings on sonography and nuclear scintigraphy are equivocal Findings of biliary atresia on MRCP include periportal thickening, which represents fibrosis, and a small gallbladder Guibaud and Lachaud32 have reported that if the extrahepatic bile ducts are normal in appearance on MRCP, then biliary atresia can be excluded In clinical practice, however, biopsy still is performed routinely to make the diagnosis of biliary atresia Alagille Syndrome In 1987, Alagille described the syndrome of arteriohepatic dysplasia This syndrome has five major components: (1) abnormal facies (large forehead, small pointed chin, hypertelorism, poorly developed nasal bridge), (2) chronic cholestasis, (3) ocular abnormalities, (4) butterfly vertebrae, and (5) pulmonary hypoplasia or stenosis Other less frequent features include growth and mental retardation, renal disturbances undertubulation, and osteopenia of bones and vascular malformations The intrahepatic component of Alagille syndrome, which is characterized by paucity of the intrahepatic ducts, may present during infancy or later in life with cholestasis.33–35 Liver biopsy in addition 459 460 Anupindi & Victoria Fig Biliary atresia A neonate with prenatal diagnosis of abdominal cyst (A) Coronal half-Fourier acquisition single-shot turbo spin echo (HASTE) T2 weighted and (B) axial HASTE T2 weighted images demonstrate mild cystic dilatation of the common bile duct (CBD) (arrow) with tortuosity of the bile duct (arrowhead) At surgery, the CBD was found to be distended, terminating in a fibrous cord (C) Intraoperative cholangiogram Contrast was injected into the gallbladder and then passed into the intrahepatic ducts The extrahepatic duct fills only proximally (arrow) No contrast entered the small bowel, confirming the diagnosis of extrahepatic biliary atresia Fig Caroli syndrome Autosomal recessive kidney disease with congenital hepatic fibrosis (A) Coronal T2 weighted half-Fourier acquisition single-shot turbo spin echo (HASTE) image in this 5-year-old patient demonstrates moderate intra- and extrahepatic biliary ductal dilatation that tapers at the level of the proximal common bile duct (arrow) (B) Axial HASTE shows fine linear areas in the subcapsular region of the liver (arrowheads), which are hyperintense to liver, consistent with hepatic fibrosis MR Cholangiopancreatography Techniques Fig Spectrum of type choledochal cysts 5-month-old patient with acholic stools (A) Transverse sonogram demonstrates an enlarged, irregular common bile duct (arrow) (B) Coronal maximal intensity projection of a respiratory-triggered T2 weighted three-dimensional fast spin echo image demonstrates mild extrahepatic dilatation of the proximal common bile duct, which tapers abruptly distally (arrow), consistent with type choledochal cyst A second infant with prenatal diagnosis of mesenteric cyst (C) Transverse sonogram demonstrates large cystic structure (arrow) in the region of the porta hepatis (D) Thick slab T2 weighted coronal oblique image demonstrates fusiform dilatation of the common bile duct (arrow) with mild dilatation of the intrahepatic ducts of the left lobe (E) Axial T2 weighted half-Fourier acquisition single-shot turbo spin echo sequence confirms the same findings but more clearly depicts dilatation of the intrahepatic ducts (arrow) to at least three of the previously mentioned features provides the definite diagnosis The MR imaging/MRCP hepatic findings of Alagille have not been reported in the literature Congenital Hepatic Fibrosis Congenital hepatic fibrosis is a heritable, developmental disorder characterized by the presence of abnormal fibrous tissue in the portal tracts.34–36 Other associated biliary anomalies include biliary cysts, Caroli disease, and choledochal cysts In most cases, hepatic fibrosis is associated with other extrahepatic findings, including renal tubular ectasia, polycystic kidney disease, renal dysplasia, and nephronophthisis Many consider congenital hepatic fibrosis and autosomal recessive polycystic disease in the same spectrum.36 Dilated biliary ducts and portal hypertension may lead to serious complications, namely gastrointestinal hemorrhage and cholangitis Although congenital hepatic fibrosis is a histologic diagnosis, MR imaging can provide a comprehensive assessment of the liver and ducts and the degree of portal hypertension Fig Choledochocele Coronal thick slab heavily T2 weighted sequence demonstrates Todani type choledochal cyst/choledochocele with localized cystic dilatation of the duodenal portion of the common bile duct (arrow) with a windsock deformity distally 461 462 Anupindi & Victoria Fig Caroli disease 7-year-old girl previously healthy who presents with massive hematemesis (A) Coronal maximal intensity projection reconstructed from three-dimensional T2 weighted SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) sequence and (B) axial half-Fourier acquisition single shot turbo spin echo T2 weighted image demonstrate marked dilatation of the extrahepatic bile duct (arrow) with moderate tortuosity and distension of the intrahepatic ducts (arrowheads) and associated cystic renal disease Based on the authors’ experience, the degree of ductal dilatation on MRCP can be extensive (Fig 6) Choledochal Cysts Choledochal cysts are not uncommon and first may be diagnosed on fetal imaging There are five types based on the Todani classification system, and all have been described well by MRCP.21,25,26,37 Most of the cysts are type 1, which is diffuse involvement of the CBD and common hepatic duct (Fig 7) Type involves isolated cysts that protrude exophytically from the CBD Type is choledochocele, which is a focal dilatation of the intraduodenal portion of the CBD (Fig 8) Type 4A involves dilatation of the intra and extrahepatic ducts, while type 4B involves only extrahepatic ducts, and Type (Caroli disease) involves only intrahepatic ducts (Fig 9) The literature has shown that MRCP is comparable or superior to ERCP and conventional cholangiography for depicting these cysts.4 Inflammatory Diseases Pancreatitis and primary sclerosing cholangitis represent the most common inflammatory conditions in children requiring MRCP application Fig.10 Chronic pancreatitis Three-year-old boy with elevated triglycerides and hypercholesterolism (A) Coronal maximal intensity projection of a T2 weighted three-dimensional fast spin echo image demonstrates an irregular and mildly distended pancreatic duct, sequela from several episodes of pancreatitis (arrow) (B) Axial fast imaging with steady state precession image reveals atrophy of the tail of the pancreas (arrowheads) Note branches emanating perpendicular from the pancreatic duct because of ductal ectasia MR Cholangiopancreatography Techniques Fig.11 Sclerosing cholangitis 13-year-old boy with long-standing abnormal liver function tests (A) Coronal maximal intensity projection acquired form three-dimensional SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) magnetic resonance cholangiopancreatography demonstrates irregular, beaded intrahepatic ducts (arrow), consistent with sclerosing cholangitis (B) Coronal contrast-enhanced T1 weighted image shows a regenerating nodule (arrow) consistent with associated cirrhosis Marked splenomegaly is also present (S) Pancreatitis is a common indication for imaging the pancreaticobiliary system in a child US and enhanced CT are usually the first lines of imaging in acute pancreatitis, as they adequately evaluate the pancreas and readily identify complications.38 There are numerous causes of acute pancreatitis in children, trauma being the most common Blunt trauma to the duodenum can lead to acute pancreatitis also In children who have chronic pancreatitis, MRCP facilitates evaluation of the ducts and is most valuable to identify congenital causes predisposing to pancreatitis, such as pancreas divisum, or complications of pancreatitis, such as strictures of the proximal common biliary or pancreatic ducts (Fig 10).39,40 Primary sclerosing cholangitis is a chronic inflammation characterized by intrahepatic and extrahepatic biliary strictures and thickened bile duct walls This disease usually presents in adolescents who have inflammatory bowel disease, usually ulcerative colitis Presenting symptoms include hyperbilirubinemia, jaundice, and abdominal pain The MRCP findings are strictures and obliterated ducts (Fig 11).41 In a study by Vitellas and Enns,24 ductal narrowing was visualized better on thickslab MRCP than on contrast cholangiography MRCP, however, has been shown to frequently overestimate the extent of stricture formation.42 Pancreatic Trauma In the evaluation of blunt pancreatic trauma, CT is the preferred study in the acute setting MRCP, however, is a valuable adjunct to CT for demonstrating lacerations of the pancreatic duct and pseudocysts.43 Pancreatic duct disruptions can be depicted best on axial curved reformations or MIPS reconstructed from a three-dimensional T2 weighted sequence in the coronal oblique plane (Fig 12) MRCP is also valuable for evaluating Fig 12 Traumatic pancreatic laceration Coronal halfFourier acquisition single-shot turbo spin echo image demonstrates interruption of the proximal pancreatic duct, consistent with transection (arrow) A large extrapancreatic fluid collection is seen at the site of injury (F) The stomach (S) is located just superior to the large fluid collection 463 464 Anupindi & Victoria Fig.13 Postsurgical stricture in a - 5-month-old status after right lobectomy for hepatic hemangioendothelioma (A) Coronal maximal intensity projection image acquired from a three-dimensional T2 weighted sequence shows mild distension of the biliary tree to the level of the left hepatic duct, where there is an abrupt cut-off (arrow) (B) Intraoperative cholangiogram confirms saccular dilatation of the bile ducts and the abrupt cut-off of the left hepatic duct (arrow) Surgical exploration revealed kinking at the origin of the left hepatic duct caused by mass effect from a regenerating left hepatic lobe postoperative complications, including duct obstruction and ductal disruption (Fig 13) BILIARY CALCULI MRCP is used commonly in the adult population for evaluating biliary ductal calculi, but it is not used widely in children, because choledocholithiasis is relatively uncommon in children Sonography is the preferred imaging study for ductal stones, but if the sonogram is nondiagnostic, MRCP may be useful Stones also can be identified incidentally on MRCP in children who have long-standing biliary obstruction and bile stasis (Fig 14) Stones as small as mm can be detected, appearing as low signal intensity abnormalities on T2 weighted sequences MRCP has been shown to be helpful in detecting both extra- and intrahepatic stones.44 PANCREATICOBILIARY NEOPLASMS Pancreatic and bile duct tumors are frequently a clinical indication for MR imaging and MRCP imaging in adults These entities, however, are rare in children.45 Tumors producing adenopathy and large tumor burden in the porta hepatic and pancreatic head region can lead to biliary obstruction Embryonal type rhabdomyosarcoma of the bile ducts is a rare but recognized tumor in children that has distinct imaging features.46 This tumor occurs in children between and years of age and is a slowly growing tumor that arises from the CBD and grows as grape-like solid or mixed cystic and solid masses along the bile ducts (Fig 15) On MR imaging/MRCP, the tumor appears as a high signal intensity mass along the course of the CBD and intrahepatic ducts The hallmark of the tumor is that it infiltrates the liver but usually does not cause biliary ductal dilatation SUMMARY Fig 14 Cholelithiasis Coronal T2 weighted half-Fourier acquisition single-shot turbo spin echo image demonstrates a cirrhotic liver with ascites and a low signal structure in the gallbladder (arrow) consistent with a gallstone MRCP has been established as a valuable and feasible tool for evaluating children with various biliary and pancreatic anomalies With the development of three-dimensional and parallel imaging techniques and T scanners, greater SNR and spatial resolution with shorter scan times can be achieved A major advantage of MRCP over CT and ERCP is the lack of ionizing radiation MR Cholangiopancreatography Techniques Fig 15 Biliary rhabdomyosarcoma 3-year-old patient with jaundice (A) Transverse sonogram at the level of the porta hepatis reveals mild intrahepatic dilatation (arrow) (B, C and D) Axial T1 weighted, T2 weighted, and fatsuppressed gadolinium-enhanced T1 weighted images demonstrate an avidly enhancing mass (arrow) arising at the level of the porta hepatis and resulting in moderate common bile duct dilatation (arrowhead) Advances in MRCP techniques and secretin-enhanced MRCP hold promise for increasing use of MRCP in children REFERENCES Wallner BK, Schumacher KA, et al Dilated biliary tract: evaluation with MR cholangiography with a T2-weighted contrast-enhanced fast sequence Radiology 1991;181:805–8 Barish MA, Yucel EK, Ferrucci JT, et al Magnetic resonance cholangiopancreatography N Engl J Med 1999;341(4):258–64 Krause D, Cercueil JP, et al MRI for evaluating congenital bile duct abnormalities J Comput Assist Tomogr 2002;26:541–52 Heller SL, Lee VS MR imaging of the gallbladder and biliary system Magn Reson Imaging Clin N Am 2005;13:295–311 Schindera ST, Merkle EM MR cholangiopancreatography: 1.5 T versus T Magn Reson Imaging Clin N Am 2007;15:355–64 Delaney L, Applegate KE, et al MR cholangiopancreatography in children: feasibility, safety, and initial experience Pediatr Radiol 2008;38:64–75 Riordan RD, Khonsari M, et al Pineapple juice as a negative oral contrast agent in magnetic resonance cholangiopancreatography: a preliminary evaluation Br J Radiol 2004;77:991–9 Braga HJ, Choti MA, et al Liver lesions: manganeseenhanced MR and dual-phase helical CT for preoperative detection and characterization comparison with receiver operating characteristic analysis Radiology 2002;223:525–31 Fisher AR, Siegelman ES Magnetic resonance imaging techniques Clin Liver Dis 2002;6:53–72 10 Bluemke DA, Sahani D, et al Efficacy and safety of MR imaging with liver-specific contrast agent: US multicenter phase III study Radiology 2005;237:89–98 11 Lee VS, Krinsky GA, et al Defining intrahepatic biliary anatomy in living liver transplant donor candidates at mangafodipir trisodium-enhanced MR cholangiography versus conventional T2 weighted MR cholangiography Radiology 2004;233:659–66 12 Zhang J, Israel GM, et al Isotropic 3D T2 weighted MR cholangiopancreatography with parallel imaging: feasibility study AJR Am J Roentgenol 2006;18:1564–70 13 Soher BJ, Dale BM, et al A review of MR physics: T versus 1.5 T Magn Reson Imaging Clin N Am 2007;15:277–90 465 466 Anupindi & Victoria 14 Fukukura Y, Fujiyoshi F, et al Pancreatic duct: morphologic evaluation with MR cholangiopancreatography after secretin stimulation Radiology 2002; 222:674–80 15 Akisik MF, Sandrasegaran K, et al Dynamic secretin-enhanced MR cholangiopancreatography Radiographics 2006;26:665–77 16 Manfredi R, Costamagna G, et al Severe chronic pancreatitis versus suspected pancreatic disease: dynamic MR cholangiopancreatography after secretin stimulation Radiology 2000;214:849–55 17 Manfredi R, Costamagna G, et al Pancreas divisum and santorinicele: diagnosis with dynamic MR cholangiopancreatography with secretin stimulation Radiology 2000;217:403–8 18 Silva AC, Friese JL, et al MR cholangiopancreatography: improved ductal distention with intravenous morphine administration Radiographics 2004;24: 677–87 19 Anupindi S, Jaramillo D Pediatric magnetic resonance imaging techniques Magn Reson Imaging Clin N Am 2002;10:189–207 20 Cravero JP, Blike GT Pediatric sedation Curr Opin Anaesthesiol 2004;17:247–51 21 Miyazaki T, Yamashita Y, et al MR cholangiopancreatography using HASTE (half-Fourier acquisition single-shot turbo spin echo) sequences AJR Am J Roentgenol 1996;166:1297–303 22 Miyazaki T, Yamashita Y, et al Single-shot MR cholangiopancreatography of neonates, infants, and young children AJR Am J Roentgenol 1998;170:33–7 23 Watanabe Y, Dohke M, et al Diagnostic pitfalls of MR cholangiopancreatography in the evaluation of the biliary tract and gallbladder Radiographics 1999;19:415–29 24 Vitellas KM, Enns RA, et al Comparison of MR cholangiopancreatographic techniques with contrastenhanced cholangiography in the evaluation of sclerosing cholangitis AJR Am J Roentgenol 2002;178: 327–34 25 Rizzo RJ, Szucs RA, et al Congenital abnormalities of the pancreas and biliary tree in adults Radiographics 1995;15:49–68 [quiz: 147–8] 26 Mortele KJ, Rocha TC, et al Multimodality imaging of pancreatic and biliary congenital anomalies Radiographics 2006;26:715–31 27 Fulcher AS, Turner MA MR pancreatography: a useful tool for evaluating pancreatic disorders Radiographics 1999;19:5–24 [discussion: 41-4]; [quiz: 148–9] 28 Kim MJ, Han SJ, et al Using MR cholangiopancreatography to reveal anomalous pancreaticobiliary ductal union in infants and children with choledochal cysts AJR Am J Roentgenol 2002;179:209–14 29 Turner MA, Fulcher AS The cystic duct: normal anatomy and disease processes Radiographics 2001;21:3–22 [questionnaire: 288–94] 30 Bret PM, Reinhold C, et al Pancreas divisum: evaluation with MR cholangiopancreatography Radiology 1996;199:99–103 31 Park WH, Choi SO, et al A new diagnostic approach to biliary atresia with emphasis on the ultrasonographic triangular cord sign: comparison of ultrasonography, hepatobiliary scintigraphy, and liver needle biopsy in the evaluation of infantile cholestasis J Pediatr Surg 1997;32:1555–9 32 Guibaud L, Lachaud A, et al MR cholangiography in neonates and infants: feasibility and preliminary applications AJR Am J Roentgenol 1998;170:27–31 33 McDaniell R, Warthen DM, et al NOTCH2 mutations cause Alagille syndrome, a heterogeneous disorder of the notch signaling pathway Am J Hum Genet 2006;79:169–73 34 Krantz ID, Piccoli DA, et al Alagille syndrome J Med Genet 1997;34:152–7 35 Piccoli DA, Spinner NB Alagille syndrome and the Jagged1 gene Semin Liver Dis 2001;21:525–34 36 Kamath BM, Piccoli DA Heritable disorders of the bile ducts Gastroenterol Clin North Am 2003;32: 857–75 vi 37 Kim WS, Kim IO, et al Choledochal cyst with or without biliary atresia in neonates and young infants: US differentiation Radiology 1998;209:465–9 38 Vaughn DD, Jabra AA, et al Pancreatic disease in children and young adults: evaluation with CT Radiographics 1998;18:1171–87 39 Shimizu T, Suzuki R, et al Magnetic resonance cholangiopancreatography in assessing the cause of acute pancreatitis in children Pancreas 2001;22:196–9 40 Benifla M, Weizman Z Acute pancreatitis in childhood: analysis of literature data J Clin Gastroenterol 2003;37:169–72 41 Vitellas KM, Keogan MT, et al Radiologic manifestations of sclerosing cholangitis with emphasis on MR cholangiopancreatography Radiographics 2000;20: 959–75 [quiz: 1108–9, 1112] 42 Vitellas KM, El-Dieb A, et al MR cholangiopancreatography in patients with primary sclerosing cholangitis: interobserver variability and comparison with endoscopic retrograde cholangiopancreatography AJR Am J Roentgenol 2002;179:399–407 43 Bosboom D, Braam AW, et al The role of imaging studies in pancreatic injury due to blunt abdominal trauma in children Eur J Radiol 2006;59:3–7 44 Kim YK, Kim CS, et al Value of adding T1 weighted image to MR cholangiopancreatography for detecting intrahepatic biliary stones AJR Am J Roentgenol 2006;187:W267–74 45 Chung EM, Travis MD, et al Pancreatic tumors in children: radiologic–pathologic correlation Radiographics 2006;26:1211–38 46 Donnelly LF, Bisset GS 3rd, et al Diagnosis please Case 2: embryonal rhabdomyosarcoma of the biliary tree Radiology 1998;208:621–3  ... T and T equipment.4,5 The goal of these sequences, in conjunction with parallel imaging, is again to shorten scan times and improve SNR and spatial resolution The technical parameters for T and. .. pressure and distension of the biliary and pancreatic ducts Silva and Friese18 have described the use of morphine during MRCP in adults to improve the visualization of small intrahepatic biliary and. .. vertebrae, and (5) pulmonary hypoplasia or stenosis Other less frequent features include growth and mental retardation, renal disturbances undertubulation, and osteopenia of bones and vascular